1.         T. Akazaki, J. Nitta, and H. Takayanagi

            "Single-Crystal Growth Of Nb Films Onto Molecular-Beam Epitaxy Grown (001)Inas"

            Appl. Phys. Lett. 59 (16), 2037-2039 (1991).

 

            ABSTRACT: Thin Nb films are grown by electron beam evaporation in an ultrahigh vacuum system on molecular beam epitaxy grown (001) InAs epitaxial layers. The Nb on InAs grows as a single-crystalline deposit at a substrate temperature of 200-degrees-C. The orientation relation is (001)Nb parallel-to (001)InAs with [110]Nb parallel-to [110]InAs, which is different from Nb growth on GaAs. The interface between Nb and InAs features a crystal-disordered layer with a thickness of 1-2 nm, which provides relaxation from lattice mismatch. Critical current measurement of Nb/InAs/Nb junctions shows that the crystal-disordered layer does not affect the superconducting characteristics of the junctions.

 

2.         H. Ando, H. Oohashi, and H. Kanbe

            "Carrier-Induced Optical Nonlinear Effects In Semiconductor Quantum-Well Wire Structure"

            J. Appl. Phys. 70 (11), 7024-7032 (1991).

 

            ABSTRACT: Carrier-induced optical nonlinearities in a GaAs quantum well wire structure are calculated within the framework of the effective mass approximation to clarify the nonlinear features of the one-dimensional (1D) system. In the calculation, the excitonic nonlinearity due to phase-space-filling, band-gap renormalization, and Coulomb screening effects is estimated on the basis of an effective 1D Coulomb potential. The 1D potential is derived, taking wire cross section into account. The change in the optical absorption for the band-to-band transition is evaluated, considering the band-filling effect and the changes in the Sommerfeld factor caused by the screening effects. The numerical results show that a blue shift of the excitonic absorption peak occurs at the absorption edge because the blue shift caused by the screening effect exceeds the red shift due to the band-gap shrinkage. In the spectral region above the band edge, where the band-to-band transition determines the optical properties, a decrease in optical absorption caused by band filling is compensated by increasing absorption, which stems from recovery of the Sommerfeld factor because of the Coulomb screening. The effect of the Coulomb interaction in a quantum wire laser is also discussed in relation to the gain spectrum in the high excitation regime. These results show that exact inclusion of the Coulomb interaction is crucial in estimating both linear and nonlinear optical properties in the 1D system.

 

3.         S. Ando, S. S. Chang, and T. Fukui

            "Selective Epitaxy Of Gaas/Algaas On (111)B-Substrates By Mocvd And Applications To Nanometer Structures"

            J. Cryst. Growth 115 (1-4), 69-73 (1991).

 

            ABSTRACT: We demonstrate the selective epitaxy of GaAs/AlGaAs rectangular structures on SiO2 stripe-masked (111)B substrates by MOCVD. The structures have an exceedingly uniform and smooth (111)B top surface and {110} sidewalls. Furthermore, little lateral overgrowth is observed. No crystal growth occurs on the SiO2 mask region. The excellent thickness uniformity and absence of lateral overgrowth are accomplished by using a high growth temperature and a low AsH3 partial pressure. Using the resultant structure, we further demonstrate the lateral growth of n-AlGaAs/GaAs modulation-doped structures on the {110} sidewalls. This leads to the formation of lateral quantum wires. In these structures, there is no size fluctuation which is commonly present when dry etching processes are used. The mechanisms accounted for the desired growth conditions in both the vertical and the lateral direction are discussed.

 

4.         L. J. Andrews, T. Mukai, N. A. Olsson, and D. N. Payne

            "Special Issue Of The Journal-Of-Lightwave-Technology On Optical Amplifiers - Foreword"

            J. Lightwave Technol. 9 (2), 145-146 (1991).

 

            ABSTRACT:

5.         G. Bjork, S. Machida, Y. Yamamoto, and K. Igeta

            "Modification Of Spontaneous Emission Rate In Planar Dielectric Microcavity Structures"

            Phys. Rev. A 44 (1), 669-681 (1991).

 

            ABSTRACT: The spontaneous emission rate and radiation pattern for a thin quantum well sheet enclosed by a one-dimensional dielectric microcavity have been calculated. By placing the sheet in the node (antinode) position of the cavity standing wave, the spontaneous emission in the direction normal to the sheet will be decreased (enhanced). In the former case the theory predicts that the spontaneous lifetime can be increased more than a factor of 10. In the latter case both theory and experiments confirm that such a simple structure can couple a substantial amount (30-90 %) of the spontaneous emission into the cavity resonant mode. In both cases, however, theory predicts that the spontaneous emission lifetime will increase for structures without guided modes.

 

6.         A. Chavezpirson, J. Yumoto, H. Ando, T. Fukui, and H. Kanbe

            "Polarization-Dependent Optical Nonlinearities In Fractional-Layer Superlattices"

            Appl. Phys. Lett. 59 (21), 2654-2656 (1991).

 

            ABSTRACT: We measure the room-temperature polarization-dependent nonlinear absorption and refractive-index spectra of a (Al0.5Ga0.5As)1/2(GaAs)1/2 fractional-layer superlattice (FLS) structure grown by metalorganic chemical vapor deposition. The anisotropic nonlinear effects between the directions parallel and perpendicular to the superlattice give rise to a nonlinear optical birefringence in the plane of the growth surface. From our measurements using a femtosecond optical pulse, we derive the magnitude and spectral shape of the nonlinear optical birefringence. We describe the basis of an all-optical polarization rotation switch using the FLS structure.

 

7.         J. L. Chern, J. K. McIver, and K. Otsuka

            "Delay-Induced Effects On Isola Type Of Steady-State Pattern In A Coupled Optical Bistable Chain"

            Phys. Lett. A 158 (5), 209-215 (1991).

 

            ABSTRACT: This study shows thai delay may not destabilize a steady state which is surrounded by unstable steady states. This is in a sharp contrast to a well-known concept, i.e. "delay will induce instability". An example is shown within the isolas' bifurcation structure and three types of steady state patterns are classified. Type I and II patterns form the isolas while type III pattern is the symmetrical solution. It is shown that the unstable type I pattern survives delay. This is the basic requirement for further development of isola chaos. However, type II and III patterns are not recovered by delay. Isola chaos will be terminated via crisis and merge to full-scale chaos. We investigate the origin of this full-scale chaos. A phenomenon related to "sensitivity of parameters" is shown. Finally we discuss the possibility of observation.

 

8.         J. B. Cole

            "The Statistical-Mechanics Of Image Recovery And Pattern-Recognition"

            Am. J. Phys. 59 (9), 839-842 (1991).

 

            ABSTRACT: Many kinds of problems in physics and engineering can be cast as optimization problems in which a solution must be picked out of a very large and "complicated" solution candidate space. The simulated annealing algorithm, which derives from statistical mechanical theory, and Bayes' theorem are introduced and it is shown how they can be combined to solve such problems. As an example, the problem of image recovery from noisy data is considered.

 

9.         J. B. Cole, H. Murase, and S. Naito

            "A Lie Group Theoretic Approach To The Invariance Problem In Feature-Extraction And Object Recognition"

            Pattern Recognit. Lett. 12 (9), 519-523 (1991).

 

            ABSTRACT: We derive a formal solution to the invariance problem and construct it using Lie group generators. Representations of these generators with respect to image data are discussed. Group theoretical obstacles to three-dimensional invariant recognition and possible solutions are considered.

 

10.       K. W. Delong, J. Yumoto, and N. Finlayson

            "Dynamics Of The Nonperiodic Discrete Self-Trapping Equation"

            Physica D 54 (1-2), 36-42 (1991).

 

            ABSTRACT: We study the dynamics of a version of the discrete self-trapping equation which describes an array of three nonlinear oscillators with nearest neighbor coupling. The reduced symmetry of this system compared to the usual system with periodic boundary conditions leads to some interesting effects which are not present in the higher symmetry case. We calculate the Lyapunov exponents for a wide variety of initial conditions, and examine some of the self-trapping properties of this particular system. We find that self-trapping of the excitation can occur on one or two of the three oscillators, and that the stability properties of certain stationary solutions extend to broad areas of neighboring trajectories in phase space.

 

11.       S. R. Friberg

            "Soliton Fusion And Steering By The Simultaneous Launch Of 2 Different-Color Solitons"

            Opt. Lett. 16 (19), 1484-1486 (1991).

 

            ABSTRACT: Two optical solitons with different center frequencies simultaneously launched into an optical fiber are considered. By numerical simulation and by experiment, it is shown that if their frequency separation is small, they will either merge into a single pulse (fusion) or form two pulses with different velocities (steering), depending on their phase difference. With a 400-m fiber and approximately 2.5-ps solitons at 1457.7 and 1460.7 nm, fusion and steering of as much as 7 ps are demonstrated.

 

12.       T. Fukui, S. Ando, Y. Tokura, and T. Toriyama

            "Gaas Tetrahedral Quantum Dot Structures Fabricated Using Selective Area Metalorganic Chemical Vapor-Deposition"

            Appl. Phys. Lett. 58 (18), 2018-2020 (1991).

 

            ABSTRACT: New GaAs quantum dot structures, called tetrahedral quantum dots (TQDs), are proposed to make a zero-dimensional electron-hole system. The TQDs are surrounded by crystallographic facets fabricated using selective area metalorganic chemical vapor deposition (MOCVD) on (111)B GaAs substrates. The calculated energy sublevel structures of zero-dimensional electrons in a GaAs TQD show large quantum size effects, because electrons are confined three dimensionally. GaAs and AlGaAs tetrahedral facet structures on (111)B GaAs substrates partially etched into a triangular shape were grown using MOCVD. Tetrahedral growth with {110} facets occurs in the triangular areas. The cathodoluminescence intensity map for GaAs tetrahedrons buried in AlGaAs shows the tetrahedral dot array.

 

13.       T. Fukui and H. Saito

            "Step-Flow Growth And Fractional-Layer Superlattices On Gaas Vicinal Surfaces By Mocvd"

            J. Cryst. Growth 115 (1-4), 61-64 (1991).

 

            ABSTRACT: (AlAs)1/2(GaAs)1/2 fractional-layer superlattices are grown on various GaAs (001) vicinal substrates by metalorganic chemical vapor deposition (MOCVD). When the substrate is misoriented to [110BAR] by 1.92-degrees and [110] by 0.10-degrees, uniform superlattice periods are observed over a large surface area by bright field transmission electron microscopy (TEM). These results suggest that ideal growth from a kink site occurs during MOCVD growth, and that the distances between kink sites are equal. On a substrate misoriented to [110] by 1.90-degrees, the superlattice periods exhibit an undulation. This shows that kink flow mode growth is not dominant in the [110] direction. On a substrate misoriented to [010] by 2.0-degrees, no superlattice period were observed. The growth mechanisms are discussed on the basis of these results.

 

14.       T. Fukui and H. Saito

            "Step-Flow Growth And Fractional-Layer Superlattices On (111bar)B Gaas Vicinal Surfaces"

            J. Cryst. Growth 107 (1-4), 231-236 (1991).

 

            ABSTRACT: Step-flow growth and fractional-layer superlattices (FLSs) on (1BAR1BAR1BAR)B GaAs vicinal surfaces are investigated. Their periodic structures are measured by X-ray superlattice satellite diffraction. When conventional MOCVD is used, FLSs cannot be grown on the (1BAR1BAR1BAR)B vicinal surfaces. However, high intensity X-ray superlattice satellites are observed for FLSs grown by flow-rate modulation epitaxy (FME) in which group III and group V raw materials were alternately supplied. The crystal quality of FLSs is also strongly affected by the misorientation direction. The relationship between step flow growth and atomic arrangements near a step is discussed.

 

15.       T. Furubayashi, K. Kinoshita, T. Yamada, and T. Matsumoto

            "Mossbauer Studies On Superconducting La1.82ca1.18(Cu0.99fe0.01)2o6"

            Physica C 185, 1231-1232 (1991).

 

            ABSTRACT: Mossbauer spectroscopy was used to study the superconducting oxide La1.82Ca1.18(Cu0.99 Fe-57(0.01))2O6 prepared under oxygen pressures of 2 atm (non-superconducting), 50 atm (T(c) = 9 K) and 400 atm (T(c) = 43 K). The spectra recorded at room temperature were paramagnetic. Iron atoms occupy mainly regular copper sites with pyramidal oxygen coordination. The measurements at 4.2 K showed that the samples prepared in 2 and 50 atm are magnetically ordered and suggested that the magnetization direction is parallel to the a, b-plane. In contrast, the magnetic ordering was largely suppressed at 4.2 K in the superconducting sample prepared in 400 atm oxygen.

 

16.       A. Furusaki, H. Takayanagi, and M. Tsukada

            "Josephson Current Through Narrow Channels"

            Physica C 185, 2585-2586 (1991).

 

            ABSTRACT: The supercurrent through a constriction is calculated both numerically and analytically for two-dimensional superconductor-semiconductor-superconductor Josephson junctions. It is found that the critical current changes stepwise as a function of the width due to the quantization of the transverse momentum in the constriction. The step height of the critical current depends both on the gap of the superconductors and on the separation between the two super-normal interfaces.

 

17.       A. Furusaki, H. Takayanagi, and M. Tsukada

            "Theory Of Quantum Conduction Of Supercurrent Through A Constriction"

            Phys. Rev. Lett. 67 (1), 132-135 (1991).

 

            ABSTRACT: The dc Josephson current through a constriction in a two-dimensional superconductor-semiconductor-superconductor junction is calculated. It is shown that when the Fermi wavelength is comparable with the width of the constriction, the critical current shows a steplike variation as a function of the width of the constriction; this is reminiscent of the quantization of the normal-state conductance of point contacts in a two-dimensional electron gas.

 

18.       I. Hashimoto, K. Odaka, T. Gatayama, and S. Yokoyama

            "Multichannel Measurements Of Magnetic Compound Action Fields Of The Median Nerve In Man"

            Electroencephalogr. Clin. Neurophysiol. 81 (5), 332-336 (1991).

 

            ABSTRACT: Magnetic compound action fields (CAFs) evoked by electrical stimulation of the median nerve at the wrist were recorded with 7-channel 2nd-order SQUID gradiometers. CAFs measured over the elbow and upper arm were biphasic with field patterns and polarities corresponding to the depolarization and repolarization fronts of the action potential volley.

 

19.       H. Hibino, Y. Shinoda, Y. Kobayashi, and K. Sugii

            "Reflection High-Energy Electron-Diffraction Studies Of Vicinal Si(111) Surfaces"

            Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 30 (7), 1337-1342 (1991).

 

            ABSTRACT: Analysis of the reflection high-energy electron diffraction (RHEED) patterns from the vicinal Si(111) surfaces misoriented to [112BAR] shows that step bunching takes place on the surface, and the surface breaks up into (111) and (331) facets. A previously unreported superstructure is found on the (331) facet. From the temperature dependence of the diffraction spot positions, this superstructure and the 7 x 7 structure on the (111) facet are shown to cause the reconstruction-induced faceting.

 

20.       Y. Hirayama, T. Saku, S. Tarucha, and Y. Horikoshi

            "Ballistic Electron-Transport In Macroscopic 4-Terminal Square Structures With High Mobility"

            Appl. Phys. Lett. 58 (23), 2672-2674 (1991).

 

            ABSTRACT: Ballistic electron transport characteristics are studied using macroscopic four-terminal square structures formed in high-mobility wafers (mu = 7.8 X 10(6) cm2/V s at 1.5 K). Ballistic transport over 200-mu-m can be detected as a negative peak in resistance around B = O T when four-terminal resistance is measured as a function of magnetic field. The ballistic mean free path (l(b)) of electrons is evaluated from the size dependence of the negative peak height. The estimated l(b) becomes 86-mu-m, which is approximately equal to a conventional mean free path calculated from carrier density and mobility of the wafer.

 

21.       Y. Hirayama, S. Tarucha, T. Saku, and Y. Horikoshi

            "Ballistic Electron-Transport In Macroscopic High Mobility Structures"

            Physica B 175 (1-3), 247-252 (1991).

 

            ABSTRACT: We investigate ballistic transport characteristics of macroscopic four-terminal structures fabricated from a high mobility (7.8 x 10(6) cm2/Vs at 1.5 K) two-dimensional electron gas at the AlGaAs-GaAs heterointerface. Ballistic electron transport over 200-mu-m is confirmed from the experimental results. The obtained transport characteristics are well explained by Landauer-Buttiker equation based analysis in spite of the terminal width being larger than 3-mu-m.

 

22.       Y. Hirayama, S. Tarucha, T. Saku, and Y. Horikoshi

            "Hall-Effect In Macroscopic Ballistic 4-Terminal Square Structures"

            Phys. Rev. B 44 (7), 3440-3443 (1991).

 

            ABSTRACT: The Hall effect is studied for 10-30-mu-m size ballistic four-terminal square structures fabricated on an Al(x)Ga(1-x)As-GaAs high-mobility modulation-doped wafer. On this scale, four-terminal square structures with sharp aperture corners are possible. The Hall resistance is not quenched and is larger than the classical linear value in a low magnetic field. It has periodic peaks corresponding to electron focusing when the terminals are narrow, and a broadening of these peaks makes a plateaulike structure when the terminals are wide.

 

23.       Y. Hirota, Y. Homma, and K. Sugii

            "Etchant Dependence Of Surface Reconstructions Of Gaas-Surfaces Prepared By Ultrasonic-Running Deionized Water-Treatment"

            Appl. Phys. Lett. 59 (26), 3410-3412 (1991).

 

            ABSTRACT: (001) GaAs surfaces treated with ultrasonic-running de-ionized water (U-RDIW) after NH4OH/H2O2/H2O etching are investigated by reflection high-energy electron diffraction (RHEED) and by x-ray photoelectron spectroscopy (XPS). RHEED observations show a spotty (1 X 1) pattern lying on the 0-th Laue circle at room temperature, a (2 X 4) streaky pattern at 310-degrees-C, and a spotty (3 X 6) pattern after annealing at 370-degrees-C. We discuss the difference in surface stoichiometry after U-RDIW between the H2SO4- and NH4OH-etched surfaces based on the results of XPS. The experimental results indicate the possibility of controlling the surface stoichiometry of the U-RDIW-treated GaAs surfaces by varying the etching solution.

 

24.       Y. Hirota, Y. Homma, and K. Sugii

            "Reflection High-Energy Electron-Diffraction Observation Of Gaas Surface-Prepared Ultrasonic Running Deionized Water-Treatment"

            Appl. Phys. Lett. 58 (24), 2794-2796 (1991).

 

            ABSTRACT: GaAs (001) surface ultrasonically cleaned under running de-ionized water (U-RDIW) is investigated by reflection high-energy electron diffraction (RHEED). The RHEED observations of U-RDIW-treated surfaces show a spotty (1 X 1) pattern at room temperature and a (2 X 1) streaky surface reconstruction pattern at 360-degrees-C. The experimental results indicate that chemically clean and damage-free GaAs surfaces can be produced by U-RDIW treatment. We discuss surface structures before/after heating using a hydrogen-terminated model.

 

25.       Y. Hirota, K. Sugii, and Y. Homma

            "Cleaning Effects Of Running Deionized Water On A Gaas Surface"

            J. Electrochem. Soc. 138 (3), 799-802 (1991).

 

            ABSTRACT: The dissolution of arsenic and gallium oxides on GaAs surfaces during running deionized water (RDIW) treatment is investigated by x-ray photoelectron spectroscopy (XPS). RDIW treatment removes arsenic oxide more rapidly than gallium oxide. The addition of ultrasonic washing to the RDIW treatment accelerates the removal of both oxides, resulting in complete removal of both oxides from a GaAs surface within 1 h. As a result, this treatment is a promising method for the cleaning of GaAs substrate surfaces. The changes in oxide thickness during these treatments are clarified by assuming a double layer structure model.

 

26.       Y. Horikoshi

            "Epitaxial-Growth Of Iii-V Compound Semiconductor Thin-Films And Their Device Applications"

            Prog. Cryst. Growth Charact. Mater. 23, 73-126 (1991).

 

            ABSTRACT:

27.       Y. Horikoshi, M. Kawashima, and N. Kobayashi

            "Optical Investigation Of Gaas Growth-Process In Molecular-Beam Epitaxy And Migration-Enhanced Epitaxy"

            J. Cryst. Growth 111 (1-4), 200-204 (1991).

 

            ABSTRACT: Epitaxial growth process of GaAs by molecular beam epitaxy and migration-enhanced epitaxy is investigated using a newly developed optical monitoring method called surface photo-absorption. This method is based on the reflectivity measurement of p-polarized light incident at the Brewster angle on the growing surface. This configuration minimizes the bulk GaAs contribution to the light reflection. The small signal from the growing surface is thus detected with a high signal-to-noise ratio. It was found that this optical method is useful for monitoring the surface chemical composition during molecular beam epitaxy, and the fractional layer growth during migration-enhanced epitaxy. An optimization of As4 deposition rate during growth is also demonstrated using the recorded surface photo-absorption signal.

 

28.       S. Imamura, R. Yoshimura, and T. Izawa

            "Polymer Channel Wave-Guides With Low-Loss At 1.3 Mu-M"

            Electron. Lett. 27 (15), 1342-1343 (1991).

 

            ABSTRACT: Highly transparent polymers in the 0.6-1.3-mu-m wavelength region have been synthesised from deuterated or halogenated methacrylate monomers. Low loss waveguides of less than 0.1 dB/cm at a wavelength of 1.3-mu-m have been fabricated using the polymers.

 

29.       K. Inoue and H. Takayanagi

            "Local Tunneling Spectroscopy Of A Nb/Inas/Nb Superconducting Proximity System With A Scanning Tunneling Microscope"

            Phys. Rev. B 43 (7), 6214-6215 (1991).

 

            ABSTRACT: Local tunneling spectroscopy for a Nb/InAs/Nb superconducting proximity system was demonstrated with a low-temperature scanning tunneling microscope. It is found that the local electron density of states in the InAs region is spatially modulated by the neighboring superconductor Nb.

 

30.       H. Isaka, M. Fujiki, M. Fujino, and N. Matsumoto

            "A New Type Of Inorganic Polymer With Ordered Sisige Sequences"

            Macromolecules 24 (9), 2647-2648 (1991).

 

            ABSTRACT:

31.       T. Ishii, T. Watanabe, K. Kinoshita, and A. Matsuda

            "Single-Crystal Growth And Superconductivity In La1.87ca1.13cu2o6"

            Physica C 179 (1-3), 39-42 (1991).

 

            ABSTRACT: Single crystals of La1.87Ca1.13Cu2O6 have been successfully grown using CuO flux. Although the electrical resistivity of the as-grown crystals is semiconducting, superconductivity appears by high oxygen pressure (approximately 300 atm) annealing. The transition temperature is between 50 K (onset) and 40 K (end point). The full magnetic shielding effect is observed under zero field cooling and the Meissner volume fraction is about 3% of that expected for an ideal diamagnet. Electrical and magnetic measurements confirm that the crystals have bulk nature of superconductivity. The anisotropies of the electrical resistivity and the coherence length are small in comparison with other copper oxide superconductors.

 

32.       M. Itoh, T. Honda, and K. Tsubaki

            "Carrier Concentration In Quantum Wires Fabricated By Ractive Ion-Beam Etching"

            Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 30 (10), 2455-2458 (1991).

 

            ABSTRACT: High-quality quantum wires with a submicron width are fabricated by a combination of electron beam lithography and selective etching by reactive ion beam etching. The carrier concentrations in these wires are evaluated as a function of gate voltage by analyzing the magnetic depopulation effect observed in the quantum wire resistance. This analysis assumes a parabolic potential profile for the wire constriction. The quantum wire capacitance calculated from the carrier concentration agrees well with the capacitance measured by the 1-MHz capacitance meter. This agreement confirmes that the carrier concentration derived from the magnetoresistance gives a good estimation to the actual quasi 1-dimensional concentration.

 

33.       W. B. Jiang, S. R. Friberg, H. Iwamura, and Y. Yamamoto

            "Collision-Induced Pulse Shortening In A Mode-Locked Linear-Cavity Nacl Color-Center Laser With An Ingaas/Inp Multiple-Quantum-Well Saturable Absorber"

            Opt. Lett. 16 (15), 1165-1167 (1991).

 

            ABSTRACT: We report collision-induced reduction of pulse widths in a linear-cavity passively mode-locked NaCl color-center laser. Colliding-pulse operation reduced the pulse widths from 800 to 430 fs. Pulses collided in the InGaAs/InP multiple-quantum-well saturable absorber if the round-trip time from the absorber to the output coupler was less than 1.3 ns, which implies carrier recombination times of that order. Measurements of the gain experienced by two successive pulses indicated partial saturation of the NaCl gain medium.

 

34.       W. B. Jiang, S. R. Friberg, H. Iwamura, and Y. Yamamoto

            "High Powers And Subpicosecond Pulses From An External-Cavity Surface-Emitting Ingaas/Inp Multiple Quantum-Well Laser"

            Appl. Phys. Lett. 58 (8), 807-809 (1991).

 

            ABSTRACT: We demonstrate that surface-emitting lasers operating in an external cavity can produce high average powers, high peak powers, and ultrashort pulses. By optical pumping of InGaAs/InP multiple quantum well samples in an external cavity, we generated 190 mW both in continuous and mode-locked operation at 1.5-mu-m. Synchronous pumping at 100 MHz yielded 7.7 ps pulses with 15 mW average power. These were shortened to 1.1 ps pulses with 64 W peak power by chirp compensation using diffraction gratings, and to 710 fs by negative group-velocity dispersion in an optical fiber.

 

35.       N. Kambe

            "Molecular-Beam-Epitaxial Growth Of Iii-Vi Layered Semiconductor Gase On Amorphous Sio2"

            J. Appl. Phys. 69 (4), 2697-2699 (1991).

 

            ABSTRACT: Crystalline thin films of III-VI layered semiconductor GaSe have been grown on amorphous SiO2 substrates using molecular-beam-epitaxy techniques. This attests possible formation of a crystalline/noncrystalline heterostructure when inactive GaSe surfaces are involved. Reflection-high-energy-electron-diffraction and (00l) x-ray diffraction results show in-plane and stacking ordering, respectively. Although the coexistence of multiple crystalline domains in plane is suggested, the photoluminescence spectra are comparable to those of a GaSe bulk single crystal. Excitonic emission with the full-width at the half magnitude of 5 nm (19 meV) is observed at 591 nm (2.10 eV) at 77 K.

 

36.       H. Kanbe, A. Chavezpirson, H. Ando, H. Saito, and T. Fukui

            "Direct Observation Of Optical Anisotropy In A Gaas/Alas Quantum-Well Wire Array"

            Appl. Phys. Lett. 58 (25), 2969-2971 (1991).

 

            ABSTRACT: Using reflectance difference spectroscopy and transmittance difference spectroscopy, optical anisotropy in a quantum well wire array is directly observed at room temperature. The quantum wire array is a fractional-layer superlattice grown by metalorganic chemical vapor deposition on a vicinal (001) GaAs substrate. The size for quantum confinement of the wires is nominally 4 X 4 nm. Polarization dependence of optical absorption and refractive index is clearly observed between the directions parallel and perpendicular to the wires.

 

37.       M. Kasu, H. Ando, H. Saito, and T. Fukui

            "Anisotropy In Photoluminescence And Absorption-Spectra Of Fractional Layer Superlattices"

            Appl. Phys. Lett. 59 (3), 301-303 (1991).

 

            ABSTRACT: Polarization-dependent photoluminescence (PL) and optical absorption spectra of (AlAs)1/2(GaAs)1/2 and (Al0.5Ga0.5As)1/2(GaAs)1/2 fractional layer superlattices (FLSs) were measured at room temperature. For the first time, it was observed that the spectra are dependent on their polarizations. The anisotropies in the PL and absorption spectra show that quantum confinement unambiguously occurs in the direction parallel to the surface, i.e., lateral quantum carrier confinement effect appears. This finding proves that FLSs are promising for novel optical devices.

 

38.       M. Kasu, H. Saito, and T. Fukui

            "Step-Density Dependence Of Growth-Rate On Vicinal Surface Of Mocvd"

            J. Cryst. Growth 115 (1-4), 406-410 (1991).

 

            ABSTRACT: The dependence of the growth rate on the step density is reported for the first time. We accurately measured the growth rate on GaAs (001) vicinal substrates with various misorientation angles. The substrates were tilted toward the [110BAR] or [110] direction with the misorientation angle ranging from 1.0-degrees to 4.0-degrees. The growth rate was derived from the superlattice period of the (AlAs)1/2(GaAs)1/2 fractional layer superlattice (FLS) measured by X-ray diffraction satellite peaks. We obtained the step density dependence of the growth rate. The results reveal that on [110BAR] misoriented surfaces the growth rate decreases slightly with decreasing misorientation angle, i.e., with decreasing step density. The growth rate decreases by 5% as the misorientation angle decreases from 4.0-degrees to 1.0-degrees. On [110] misoriented surface with the same misorientation angle, the growth rates scatter, ranging about +/- 2% from run to run. These results for [110BAR] misoriented surfaces can be explained by a simple adsorption/desorption rate model, taking into account the rate for the group III atoms to desorb from the surface (1/tau(d)), as well as the rate for the group III atoms to hop to adjoining sites (1/tau(s)). As the misorientation angle decreases, the terrace width increases, and the mean time of migration of group III atoms to reach the site steps after adsorption at the surface increases. Therefore, the possibility of desorption increases, and the growth rate decreases slightly. A Monte Carlo simulation using this model fits the experimental results.

 

39.       H. Katsuno and A. O. Mendelzon

            "Propositional Knowledge Base Revision And Minimal Change"

            Artif. Intell. 52 (3), 263-294 (1991).

 

            ABSTRACT: The semantics of revising knowledge bases represented by sets of propositional sentences is analyzed from a model-theoretic point of view. A characterization of all revision schemes that satisfy the Gardenfors rationality postulates is given in terms of minimal change with respect to an ordering among interpretations. Revision methods proposed by various authors are surveyed and analyzed in this framework. The correspondences between Gardenfors-like rationality postulates and minimal changes with respect to other orderings are also investigated.

 

40.       T. Kawabata, T. Hanazawa, K. Itoh, and K. Shikano

            "Japanese Phonetic Typewriter Using Hmm Phone Recognition And Stochastic Phone-Sequence Modeling"

            Ieice Transactions On Communications Electronics Information And Systems 74 (7), 1783-1787 (1991).

 

            ABSTRACT: A phonetic typewriter is an unlimited-vocabulary continuous speech recognition system recognizing each phone in speech without the need for lexical information. This paper describes a Japanese phonetic typewriter system based on HMM phone recognition and syllable-based stochastic phone sequence modeling. Even though HMM methods have considerable capacity for recognizing speech, it is difficult to recognize individual phones in continuous speech without lexical information. HMM phone recognition is improved by incorporating syllable trigrams for phone sequence modeling. HMM phone units are trained using an isolated word database, and their duration parameters are modified according to speaking rate. Syllable trigram tables are made from a text database of over 300,000 syllables, and phone sequence probabilities calculated from the trigrams are combined with HMM probabilities. Using these probabilities, to limit the number of intermediate candidates leads to an accurate phonetic typewriter system without requiring excessive computation time. An interpolated n-gram approach to phone sequence modeling, is shown to be more effective than a simple trigram method.

 

41.       K. Kinoshita, F. Izumi, T. Yamada, and H. Asano

            "Neutron-Diffraction Study Of Superconducting La1.82ca1.18cu2o6"

            Physica C 185, 537-538 (1991).

 

            ABSTRACT: La1.82Ca1.18Cu2O6 is superconducting if it is synthesized under high O2 pressure of more than 10 atm. Crystal structures of superconducting and nonsuperconducting La1.82Ca1.18Cu2O6 +/- delta-synthesized under 400- and 2-atm O2, respectively, were refined by Rietveld analysis of TOF neutron powder diffraction data. Slight differences are observed in occupation factors of La and Ca sites as well as in that of 2b site oxygen O(3). Cu-O(1) and Cu-O(2) bond lengths differ little between the two samples.

 

42.       K. Kinoshita, H. Shibata, and T. Yamada

            "Crystal-Structure And Superconducting Properties Of La1.85ca1.15cu2o6+Delta - Comparison With Nonsuperconducting La1.85ca1.15cu2o6-Delta And La1.85sr1.15cu2o6+Delta"

            Physica C 176 (4-6), 433-440 (1991).

 

            ABSTRACT: La1.85Ca1.15Cu2O6+delta becomes a superconductor when synthesized under high O2 pressure although La1.85Sr1.15Cu2O6+delta is not. The crystal structures of both compounds are determined by Rietveld analysis of X-ray diffraction data as a function of O2 pressure during synthesis. The ordering of La and Ca sites increases with increasing O2 pressure during synthesis for La1.85Ca1.15Cu2O6+delta but not for La1.85Sr1.15Cu2O6+delta. The interatomic distance between Cu and apical site oxygen is shorter in La1.85Sr1.15Cu2O6+delta than in La1.85Ca1.15Cu2O6+delta even though lattice parameter c is longer in La1.85Sr1.15Cu2O6+delta. The relationship between such crystal structure and superconductivity in La1.85Ca1.15Cu2O6+delta is discussed by comparison with nonsuperconducting La1.85Ca1.15Cu2O6-delta and La1.85Sr1.15Cu2O6+delta.

 

43.       M. Kitagawa and M. Ueda

            "Nonlinear-Interferometric Generation Of Number-Phase-Correlated Fermion States"

            Phys. Rev. Lett. 67 (14), 1852-1854 (1991).

 

            ABSTRACT: We propose a nonlinear-interferometric scheme for generating two fermion states correlated in particle number or in wave phase. This scheme can be used for surpassing either the standard quantum limit of the number-partition noise or that of the interferometric phase sensitivity, up to a factor of the order of (total particle number)1/3. A possible experimental scheme in a mesoscopic system is discussed.

 

44.       K. Kitazawa, Y. Tomioka, T. Hasegawa, K. Kishio, M. Naito, T. Matsushita, I. Tanaka, and H. Kojima

            "Anomalous Magnetic Behaviors Of The Cuprate Superconductors - Meissner Effect, Hc1 And Hc2"

            Supercond. Sci. Technol. 4, S35-S42 (1991).

 

            ABSTRACT: In order to elucidate whether the superconductivity of the cuprate HTSC is "normal" or "abnormal", systematic studies have been performed on the Meissner effect, lower and higher critical fields. The Meissner fraction is strongly dependent on the size of sample and on the field, which is explained by a novel model considering the sharp increase in the vortex pinning force while the flux expulsion process proceeds as T is lowered. Another new method has been proposed to determine H(c1) from the magnetization curve above H(c1), based on which the abrupt upturn of the H(c1)-T curve frequently reported in the low T region has been attributed to the error induced by the strong pinning. The ambiguity associated with the H(c2)-T curve is discussed in terms of the "giant fluctuation" of superconductivity.

 

45.       N. Kobayashi and Y. Horikoshi

            "Chemical-Shift In Optical Reflection Spectra Observed During Iii-V-Semiconductor Metalorganic Chemical Vapor-Deposition Growth By Surface Photoabsorption Method"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (8B), L1443-L1446 (1991).

 

            ABSTRACT: Spectral dependence of optical reflection from a growing surface is measured in situ during metalorganic chemical vapor deposition of As-based III-V semiconductors, InAs, GaAs, AlAs and AlGaAs by surface photo-absorption method. When one monolayer of group III atom is deposited on an As-stabilized surface, the spectral dependence of reflectivity change shows a chemical shift in the visible light region. The spectrum is red-shifted in the order of AlAs, AlGaAs, GaAs and InAs. The photon energy when the spectrum curve is rising correlates well with the heat of formation in group III atom-As tetrahedral bond, and is almost independent of the underlying layer composition. This result supports the assumption that the observed reflectivity difference between group III atom surface and As-stabilized surface in the visible light region is mainly caused by the photo-absorption process of the surface III-As chemical bond.

 

46.       N. Kobayashi and Y. Horikoshi

            "Pyrolysis Of Trimethylgallium On (001) Gaas Surface Investigated By Surface Photoabsorption"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (3A), L319-L321 (1991).

 

            ABSTRACT: We directly observe the process of CH3 desorption from a GaAs surface reacted with trimethylgallium (TMG), using the surface photo-absorption method. After supply of TMG onto the As-stabilized (001) GaAs surface in H2 carrier gas, the reflectivity increases and saturates during H2 purging at substrate temperatures below 500-degrees-C. The observed reflectivity change corresponds to the formation of the Ga metal surface caused by CH3 desorption from the CH3-terminated surface. The CH3 desorption can be described by first-order kinetics, and the desorption rate constant is 2 x 10(-2) s-1, i.e., a lifetime of 50 s at 485-degrees-C. This is long enough to support the well-accepted mechanism of atomic layer epitaxy, i.e., the inability of the excess TMG to adsorb when supplied to the CH3-terminated surface.

 

47.       N. Kobayashi and Y. Kobayashi

            "As And P Desorption From Iii-V Semiconductor Surface In Metalorganic Chemical Vapor-Deposition Studied By Surface Photoabsorption"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (10A), L1699-L1701 (1991).

 

            ABSTRACT: As and P desorption processes from (001) oriented GaAs, InAs, GaP, and InP surfaces during metalorganic chemical vapor deposition are investigated by surface photo-absorption. The reflectivity varies from that of a group V stabilized surfaces, formed by the supply of AsH3 or PH3, to that of a group III metal surface during the desorption of group V species in hydrogen carrier gas. This reflectivity change can be described by first-order kinetics. The rate equation including the activation energy can be obrained from the Arrhenius plot of the desorption rate constants. The desorption rate increases in the order of GaP, GaAs, InAs, and InP in the substrate temperature range of 400 approximately 640-degrees-C. The observed desorption activation energies suggest that the desorption species are As2 for GaAs (450 approximately 560-degrees-C) and InAs (400 approximately 460-degrees-C), P2 for GaP (500 approximately 620-degrees-C) and InP (below 390-degrees-C), and P for InP (above 390-degrees-C).

 

48.       N. Kobayashi, T. Makimoto, Y. Yamauchi, and Y. Horikoshi

            "Insitu Monitoring Of Gaas Growth-Process In Movpe By Surface Photoabsorption Method"

            J. Cryst. Growth 107 (1-4), 62-67 (1991).

 

            ABSTRACT: Surface photo-absorption (SPA) is a newly developed in-situ optical monitoring technique for the epitaxial growth process. This method is based on the reflectivity measurement of p-polarized light incident at the Brewster angle. This configuration minimizes the bulk GaAs contribution to the total light reflection. The small change in reflected light intensity between Ga and As atomic surfaces during GaAs growth is thus detected with a high signal-to-noise ratio. By using this characteristic, GaAs growth rate can be monitored in-situ on an atomic scale. In addition to the in-situ monitoring of growth rate, the decomposition processes of Ga and As precursors in MOVPE can be studied by SPA. We demonstrate an investigation of the decomposition process of Ga organometallic, and discuss the growth mechanism of atomic layer epitaxy.

 

49.       N. Kobayashi, Y. Yamauchi, and Y. Horikoshi

            "Insitu Optical Monitoring Of Pyrolysis Process On Substrate Surface In Gaas Mocvd"

            J. Cryst. Growth 115 (1-4), 353-358 (1991).

 

            ABSTRACT: We investigated the pyrolysis process of trimethylgallium (TMG) and As precursors of organo-arsenics and arsine on a (001) GaAs surface by the surface photo-absorption method in metalorganic chemical vapor deposition. For the pyrolysis of TMG, we directly observed the CH3 desorption from the GaAs surface reacted with TMG. From the CH3 desorption kinetics, we determined that the CH3-terminated surface causes self-limitation of the growth rate in atomic layer epitaxy because the excess TMG cannot adsorb. For the pyrolysis of As precursors, we estimated the pyrolysis activation energies. We show that diethylarsenic hydride and tert-butyl arsine are promising precursors as an alternative source of AsH3 because of their low pyrolysis activation energies.

 

50.       J. T. Kucera, J. D. Perkins, K. Uwai, J. M. Graybeal, and T. P. Orlando

            "Detection Of Ozone Using A Silver Coated Quartz Crystal Rate Monitor"

            Rev. Sci. Instrum. 62 (6), 1630-1632 (1991).

 

            ABSTRACT: A technique to measure ozone fluxes of 10(14)-10(16) cm-2 s-1 using a thin silver film deposited on a quartz-crystal deposition-rate monitor is described. The technique involves measuring the rate of mass increase of the silver film due to oxidation when it is first exposed to ozone. Ozone is found to be an extremely efficient oxidant for silver at room temperature. By establishing an independent measure of the incident ozone flux the product of our ozone purity and intrinsic detection efficiency has been determined to be 26 +/- 5%.

 

51.       S. Kurihara

            "Dissipation In The Phase Dynamics Of Small Josephson-Junctions"

            Physica C 185, 2527-2528 (1991).

 

            ABSTRACT: The microscopic theory of Josephson junction due to Ambegaokar, Eckern, and Schon is generalized to allow for the spatial variation of the superconducting order parameter in the vicinity of the junction plane, and to allow the coupling of phase difference to the external electromagnetic field. A few mechanisms of dissipation in phase dynamics are discussed. Leakage resistance observed down to lowest temperatures is explained on the basis of our calculation.

 

52.       Y. Lai, H. A. Haus, and Y. Yamamoto

            "Squeezed Vacuum From Amplitude Squeezed States"

            Opt. Lett. 16 (19), 1517-1519 (1991).

 

            ABSTRACT: Squeezed vacuum permits adjustment of its relative phase to a chosen signal. If the signal is used as the probe in an interferometric measurements, the signal-to-noise ratio can be improved. We propose a system that generates squeezed vacuum, which consists of a laser diode that produces amplitude squeezed states and is phase-locked to a coherent signal, and an alternate system consisting of two phase-locked laser diodes.

 

53.       Y. Maeda and K. Takei

            "Compositional Inhomogeneities In Co-Cr-Ta/Cr Films For Longitudinal Magnetic Recording"

            IEEE Trans. Magn. 27 (6), 4721-4723 (1991).

 

            ABSTRACT: The change in compositional distribution of sputtered Co-12at.% Cr-2at.% Ta films deposited on Cr underlayers is investigated as a function of substrate temperature, using spin-echo Co-59 nuclear magnetic resonance. It is observed that a highly Co-rich component with an estimated Co content of about 97 at.% precipitates as the substrate temperature increases from 25 to 250-degrees-C. The compositional microstructure observation suggests compositional separation within grains having Cr-enriched grainboundaries. The precipitation accords with an increase in coercivity and a decrease in coercive squareness and media noise. The compositional inhomogeneities observed in Co-Cr based alloy films for either longitudinal or perpendicular recording media are thought to be effective in promoting the change from a continuous structure to a particulate structure suitable for high density magnetic recording.

 

54.       T. Makimoto, K. Kurishima, T. Kobayashi, and T. Ishibashi

            "Inp/Ingaas Double Heterojunction Bipolar-Transistors Grown On Si"

            Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 30 (12B), 3815-3817 (1991).

 

            ABSTRACT: The first InP/InGaAs double heterojunction bipolar transistors on Si substrates were grown by metalorganic chemical vapor deposition. The transistor with an InP buffer layer thickness of 4-mu-m exhibited high current gains of more than 250 and an ideality factor of 1.3. (The base doping concentration and its thickness were 1.5 x 10(19) cm-3 and 700 angstrom, respectively.) The characteristics of the DHBT on Si with the 4-mu-m buffer layer are comparable to those of transistors on InP substrates.

 

55.       N. Matsumoto and H. Teramae

            "Abinitio Studies On Silicon-Compounds.3. The Trans-Gauche Mixed Structure Of Parent Polysilane"

            J. Am. Chem. Soc. 113 (12), 4481-4483 (1991).

 

            ABSTRACT: Ab initio crystal orbital calculations are performed on the electronic structures of parent polysilanes having a unit cell periodicity consisting of n trans links and one gauche link (GT(n)) and having their combined structures (GTGT(m)). Koopmans' ionization potential, vertical electron affinity, and effective mass of electron and hole are systematically estimated for n = 1, 3, 5, 7, 9, and m = 3, 5. The results show that the gauche links only slightly disturb sigma-conjugation. Both electrons and holes are not confined to the trans segments but are highly delocalized along an entire chain.

 

56.       A. Middeldorp and Y. Toyama

            "Completeness Of Combinations Of Constructor Systems"

            Lect. Notes Comput. Sci. 488, 188-199 (1991).

 

            ABSTRACT: A term rewriting system is called complete if it is both confluent and strongly normalizing. Barendregt and Klop showed that the disjoint union of complete term rewriting systems does not need to be complete. In other words, completeness is not a modular property of term rewriting systems. Toyama, Klop and Barendregt showed that completeness is a modular property of left-linear TRS's. In this paper we show that it is sufficient to impose the constructor discipline for obtaining the modularity of completeness. This result is a simple consequence of a quite powerful divide and conquer technique for establishing completeness of such constructor systems. Our approach is not limited to systems which are composed of disjoint parts. The importance of our method is that we may decompose a given constructor system into parts which possibly share function symbols and rewrite rules in order to infer completeness. We obtain a similar technique for semi-completeness, i.e. the combination of confluence and weak normalization.

 

57.       M. Mitsunaga and N. Uesugi

            "Linear And Nonlinear Spectroscopy Of Eu-3+ In Crystals"

            J. Lumines. 48-9, 459-462 (1991).

 

            ABSTRACT: Linear and nonlinear spectroscopic studies on the 7F0-5D2, -5D1, and -5D0 transitions of Eu3+ ions doped in YAlO3. YAG (Y3Al5O12), LaF3 and Y2O3 crystals are reported based on photoluminescence (PL) and photon echo (PE) measurements. Relaxation dynamics of the optically excited ions were investigated from the PL spectra and the wavelength-dependent PL decay time measurements. Two-pulse photon echoes were observed for the first time for these transitions and all the echoes were identified to be long-lived, with the storage time ranging from minutes to hours. Recently developed novel coherent transients using these samples are also reported. Specific stress is put upon the cw photon echo which enables a single shot measurement of the homogeneous dephasing time and the sublevel splitting frequencies of a medium.

 

58.       M. Mitsunaga, R. Yano, and N. Uesugi

            "Time-Domain And Frequency-Domain Hybrid Optical Memory - 1.6-Kbit Data-Storage In Eu3+ - Y2sio5"

            Opt. Lett. 16 (23), 1890-1892 (1991).

 

            ABSTRACT: We propose and demonstrate a novel type of frequency-selective optical memory that writes and reads the data in both the time domain and the frequency domain. Temporal 16-bit data were stored by accumulated-photon-echo bit-by-bit storage at 103 frequency addresses within the inhomogeneous line of the 7F0-5D0 transition of Eu3+:Y2SiO5, which yields a total memory capacity of 1.6 kbits in a single spot of 240-mu-m diameter. The keys to the success of this experiment are this material's long dephasing time and lack of spectral diffusion.

 

59.       M. Mitsunaga, R. Yano, and N. Uesugi

            "Spectrally Programmed Stimulated Photon-Echo"

            Opt. Lett. 16 (4), 264-266 (1991).

 

            ABSTRACT: A stimulated photon echo has been observed from the artificially modulated inhomogeneous distribution of a medium. A cryogenic Eu3+:YAlO3 sample with a quasi-persistent hole lifetime is exposed to a frequency-scanned and intensity-modulated cw laser for multiple hole burning. A coherent burst equivalent to the stimulated photon echo is obtained by triggering this sample by a pulsed laser. We demonstrate further that any desired transient pulse shape can, in principle, be obtained by appropriate frequency-domain programming, which opens the way to a novel type of optical memory.

 

60.       M. Naito

            "A Study Of The Compositional Dependence Of The Quality Of Insitu Grown Ybacuo Films In E-Beam Coevaporation"

            Physica C 185, 1977-1978 (1991).

 

            ABSTRACT: In-situ growth of YBaCuO thin films has bee performed in the UHV E-beam coevaporation system with careful control of the evaporation rates of metal based on electron impact emission rate monitors, which enables systematic investigation of the compositional dependence of the quality of grown films. The results show that best quality films can be obtaine in a well defined and narrow compositional range, suggesting that stringent rate control is essential for MBE growth of oxide superconductor films.

 

61.       H. Nakano, T. Akazaki, J. Nitta, and H. Takayanagi

            "Thickness Dependence Of Cooperon Lifetime In Quasi-2-Dimensional Inas Films"

            Solid State Commun. 80 (4), 251-253 (1991).

 

            ABSTRACT: The film thickness dependences of Cooperon lifetime tau-epsilon and spin-orbit scattering time tau-so are investigated experimetally by using the weak localization method. The samples are MBE-grown n-doped InAs films of various thicknesses and with the same material parameters. All the films can be considered as quasi-two-dimensional films. Tau-epsilon increases linearly with thickness, and tau-so depends only slightly on thickness. This result confirms the Cooperon lifetime theory of Altshuler et al.

 

62.       H. Nakano, Y. Ishida, and T. Yanagawa

            "Energy Relaxation And Dephasing Dynamics Of Colored Filter Glasses"

            Appl. Phys. Lett. 59 (24), 3090-3092 (1991).

 

            ABSTRACT: The energy relaxation and the dephasing time constants of colored filter glass are measured as functions of temperature and the wavelength of the incident light by degenerate four-wave mixing. To investigate the influence of the photodarkening effect on the relaxation time constants, fresh and photodarkened samples are measured. The two samples have almost the same dephasing time constants but their energy relaxation time constants are quite different.

 

63.       H. Nakano and J. Sakai

            "Transient Phase Conjugation In A 2-Level System"

            IEEE J. Quantum Electron. 27 (11), 2495-2504 (1991).

 

            ABSTRACT: An analytical expression for conjugate signals is developed for a case where three rectangular pulses with the same center frequency are injected into a two-level system. The Maxwell's equation is solved with the slowly varying envelope approximation and with the perturbative third order nonlinear polarization expression of a two-level system. Numerical examples are discussed in such a way that the input pulsewidth is changed relative to the energy relaxation and dephasing times. As the optical pulsewidth becomes short, ripples appear in the signal pulse due to the beat between the optical field and the resonant oscillation of the atomic system.

 

64.       H. Nakano and H. Takayanagi

            "Quasi-Particle Interferometer Controlled By Quantum-Correlated Andreev Reflection"

            Solid State Commun. 80 (12), 997-999 (1991).

 

            ABSTRACT: We propose a quasiparticle interferometer for experimentally confirming the predicted phase interaction between a, quasiparticle and a superconducting state at the superconductor- normal-metal (S-N) interface. The phase interaction is caused by Andreev reflection. The proposed interferometer consists of a Josephson junction and a Y-junction composed of normal electron waveguides. In the setup, the phase interaction due to Andreev reflection affects the resistance across the end of a waveguide and an electrode of the Josephson junction. Thus the amount of supercurrent flowing through the Josephson junction can control the resistance.

 

65.       S. Nakata, Y. Hirayama, S. Tarucha, and Y. Horikoshi

            "Transport Characteristics Of Algaas/Gaas Wires Fabricated By Focused Ga-Ion-Beam Implantation"

            J. Appl. Phys. 69 (6), 3633-3640 (1991).

 

            ABSTRACT: Electron transport was studied in AlGaAs/GaAs wires fabricated using focused Ga-ion-beam implantation. Single-wire samples 0.2-10-mu-m wide and 20-mu-m long were prepared with various ion doses ranging 2 X 10(11)-4 X 10(12) cm-2; multiple-wire samples 0.1-0.3-mu-m wide and 10-mu-m long were prepared with an ion dose of 2 X 10(11) cm-2. Electron mobility is reduced in the narrow wires because of the implantation-induced damage, and this mobility degradation is diminished by reducing the ion dose. These behaviors are consistently explained in terms of a diffusive scattering effect inside the channel and at the sidewall of the channel. Mobility in wires with the 2 X 10(11) cm-2 ions is predominantly determined by the sidewall specularity. A 0.2-mu-m-wide wire with this ion dose exhibits a mobility of 2 X 10(5) cm2/(V s) and a specularity above 0.8. These values exceed those previously reported for wires fabricated using ion implantation and probably arise from the annealing employed in the present work. Conductance steps are observed with a single 0.2-mu-m-wide wire, and enhanced transconductance steps occur in multiple-wire samples. These behaviors are related to mobility modulation that occurs when one-dimensional subbands cross the Fermi level.

 

66.       S. Nishida and T. Sato

            "Positive Motion Aftereffect Induced By A Bandpass Random Dot Kinematogram"

            Invest. Ophthalmol. Vis. Sci. 32 (4), 827-827 (1991).

 

            ABSTRACT:

67.       T. Nishikawa, N. Uesugi, and J. Yumoto

            "Parametric Superfluorescence In Ktiopo4 Crystals Pumped By 1-Ps Pulses"

            Appl. Phys. Lett. 58 (18), 1943-1945 (1991).

 

            ABSTRACT: Parametric superfluorescence in KTiOPO4 crystals pumped by 1 ps pulses is demonstrated using an amplified synchronous mode-locked dye laser. The tuning range of the output pulses is from 0.93 to 1.59-mu-m. The maximum output power at the degenerate wavelength of 1.2-mu-m is 0.85-mu-J, and a conversion efficiency of 9.9% is obtained. Height gain under phase mismatching broadens the spectral bandwidths of the output pulses.

 

68.       O. Niwa, M. Morita, and H. Tabei

            "Highly Sensitive And Selective Voltammetric Detection Of Dopamine With Vertically Separated Interdigitated Array Electrodes"

            Electroanalysis 3 (3), 163-168 (1991).

 

            ABSTRACT: Highly sensitive (10(-8) mol/dm3) and selective voltammetric detection of dopamine can be carried out with a closely spaced planar interdigitated array (IDA) or vertically separated new IDA electrodes. The sensitivity of dopamine was improved up to 10(-8) mol/dm3 as a result of high collection efficiency and redox cycling, because twin electrodes with a very small gap make it possible to collect most of the active species oxidized at adjacent electrodes and then to return them to dopamine by reverse reduction before the chemical reaction has terminated. The influence of L-ascorbic acid, which interferes with the detection of catecholamines, may be removed by oxidizing it at one electrode, because the oxidized acid converts rapidly to an electrochemically inactive species and is not detected at the other electrode. Dopamine was detected quantitatively in the presence of 10-fold excess of L-ascorbic acid in the same solution.

 

69.       S. Nohara, H. Namatame, H. Matsubara, M. Fujisawa, M. Naitou, S. Tanaka, H. Negishi, M. Inoue, H. Sakamoto, A. Misu, and S. Suga

            "Angle-Resolved Inverse Photoemission Spectra Of Layered 1t-Vse2, 1t-Tis2, 1t-Tas2, 2h-Nbse2 And 2h-Tase2"

            J. Phys. Soc. Jpn. 60 (11), 3882-3892 (1991).

 

            ABSTRACT: Angle-resolved inverse photoemission spectra have been measured at room temperature on the layered transition metal dichalcogenides, 1T-VSe2, 1T-TiS2, 1T-TaS2, 2H-NbSe2 and 2H-TaSe2, in the isochromat mode with a detection photon energy of 9.4 eV. Their energy dispersion curves are obtained along symmetry directions in the Brillouin zone and compared with theoretical band calculations.

 

70.       K. Nozawa and Y. Horikoshi

            "Low Threading Dislocation Density Gaas On Si(100) With Ingaas/Gaas Strained-Layer Superlattice Grown By Migration-Enhanced Epitaxy"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (4B), L668-L671 (1991).

 

            ABSTRACT: This paper reports on a new approach for reducing the threading dislocation density in GaAs on Si. We have used In(x)Ga(1-x)As/GaAs strained-layer superlattices (SLSs) grown on GaAs/Si at 300-degrees-C by migration-enhanced epitaxy as threading dislocation barriers. Different from conventional high-temperature-grown SLSs, the low-temperature-grown SLSs are only slightly relaxed by misfit dislocation formation at GaAs/SLS interfaces. Thus, considerable strain can be accumulated in SLS. In addition, new threading dislocation generation due to the misfit dislocation can be suppressed. These factors lead to effective threading dislocation bending and to significant reduction in the dislocation density. For the samples with a SLS of x = 0.3, the average etch-pit density is 7 x 10(4) cm-2, which is the lowest value ever reported.

 

71.       M. Ogawa and S. Ono

            "Transformation Of Strictness-Related Analyses Based On Abstract Interpretation"

            Ieice Transactions On Communications Electronics Information And Systems 74 (2), 406-416 (1991).

 

            ABSTRACT: This paper newly proposes HOMomorphic Transformer (HOMT) in order to formalize relations among strictness-related analyses (SRAs) on first-order functional programs. A HOMT is defined to be a composition of special instances of abstract interpretation, and has enough ability to treat known SRAs including head/tail/total strictness detection on nonflat domains. A set of HOMTs, furthermore, is an algebraic space such that some composition of HOMTs can be reduced to a simpler HOMT. This structure gives a transformational mechanism between various SRAs, and further clarifies the equivalence and the hierarchy among them. First, we show a construction of a HOMT as a composition of Unit-HOMTs (U-HOMTs) which are specified by quadruplet representations. Second, algebraic relations among HOMTs are shown as reduction rules among specific pairs of quadruplet representations. Thus, hierarchy among HOMTs can be clarified by finding some adequate quadruplet representation which bridges a HOMT to the other. Third, various SRAs are formalized as HOMTs in either forward or back-ward manners. They are also shown to be safe under unified discussions. Finally, their equivalence and hierarchy are examined in terms of an algebraic structure of HOMTs.

 

72.       T. Ogawa and T. Takagahara

            "Optical-Absorption And Sommerfeld Factors Of One-Dimensional Semiconductors - An Exact Treatment Of Excitonic Effects"

            Phys. Rev. B 44 (15), 8138-8156 (1991).

 

            ABSTRACT: We investigate theoretically excitonic effects on the optical properties of one-dimensional (1D) semiconductors. In particular, absorption spectra near a band edge are exactly calculated within the effective-mass approximation for the 1D system with a direct allowed or forbidden gap. We employ two kinds of interaction potentials between an electron and a hole describing a modified Coulomb interaction and a short-range interaction, both of which are free from the well-known divergence problem of the 1D Coulomb system. The Sommerfeld factor, which is the absorption intensity ratio of the unbound (continuum) exciton to the free-electron-hole pair above the band edge, is found to be smaller than unity for the direct allowed transition, in striking contrast to the 3D and 2D cases. This peculiar feature is interpreted in terms of the anomalously strong concentration of the oscillator strength on the lowest discrete exciton state. On the other hand, for the direct forbidden transition, the Sommerfeld factor in the 1D system is larger than unity and shows similar behavior to those in the 3D and 2D cases. These properties hold irrespective of the interaction range of the electron-hole attractive potential. The feasibility of the model potentials is examined, and the Coulomb potential having a cusp-type cutoff is found to be the most effective to describe the potential in an actual semiconductor wire. A dielectric effect in the wire structure is shown to enhance these peculiar features of the 1D system.

 

73.       T. Ogawa and T. Takagahara

            "Interband Absorption-Spectra And Sommerfeld Factors Of A One-Dimensional Electron-Hole System"

            Phys. Rev. B 43 (17), 14325-14328 (1991).

 

            ABSTRACT: Optical absorption spectra are exactly calculated for direct interband transitions in a one-dimensional (1D) electron-hole system within the effective-mass approximation. We employ a modified Coulomb potential between an electron and a hole to avoid the well-known divergence problem in the 1D system. The Sommerfeld factor, which is the absorption intensity ratio of the unbound exciton to the free electron-hole pair above the band edge, is found for the first time to be less than unity for the direct allowed transition in striking contrast to the three- and two-dimensional cases. This feature can be understood in terms of anomalously strong concentration of oscillator strength on the lowest 1D exciton state.

 

74.       T. Ogawa, M. Ueda, and N. Imoto

            "Generation Of The Schrodinger-Cat State By Continuous Photodetection"

            Phys. Rev. A 43 (11), 6458-6461 (1991).

 

            ABSTRACT: Nonunitary time evolution of an initially highly squeezed state under continuous photon-number measurement is investigated using the quasiprobability distribution. It is found that the measured quantum state bifurcates into two macroscopically distinguishable states upon the detection of a single photon, while preserving purity by feeding back real-time readout information.

 

75.       T. Ogawa, M. Ueda, and N. Imoto

            "Measurement-Induced Oscillations Of A Highly Squeezed State Between Super-Poissonian And Sub-Poissonian Photon Statistics"

            Phys. Rev. Lett. 66 (8), 1046-1049 (1991).

 

            ABSTRACT: A general quantum theory of continuous photodetection is applied to an initially squeezed state to clarify effects of quantum-mechanical measurement backaction on a highly nonclassical field. The remaining photon field is found to oscillate in time between super- and sub-Poissonian photon statistics due to the backaction of the photon-number measurement.

 

76.       T. Ohno and E. Yamaguchi

            "Energetics Of Dx-Center Formation In Gaas And Alxga1-Xas Alloys - Comment"

            Phys. Rev. B 44 (12), 6527-6529 (1991).

 

            ABSTRACT: The prediction of Chadi and Chang [Phys. Rev. B 39, 10063 (1989)] that the DX center in GaAs is a negatively charged defect is investigated. It is found from ab initio self-consistent pseudopotential calculations that the proposed negatively charged center is a metastable state and not a ground state at hydrostatic pressures up to 60 kbar.

 

77.       K. Ohta, T. Okamoto, and K. Koyama

            "Membership Authentication For Hierarchical Multigroups Using The Extended Fiat-Shamir Scheme"

            Lect. Notes Comput. Sci. 473, 446-457 (1991).

 

            ABSTRACT: We propose two membership authentication schemes that allow an authorized user to construct one master secret key for accessing the set of hierachically ordered groups defined by the user, without releasing any private user information. The key allows the user to prove his membership of his true groups and all lower groups, without revealing his name or true groups. The user can calculate the secret member information needed to access a group from his master secret key, and can convince a verifier using the extended Fiat-Shamir scheme. Each of two proposed schemes can generate the master secret key. To ensure the user's privacy, one uses the blind signature and pseudonym encryption techniques, and the other uses Euclid's algorithm. Because each user stores only one master secret key, memory usage is very efficient. Moreover, verifiers can check membership validity using public information independent of the number of users in an off-line environment. Therefore, our schemes are suitable for smart card applications.

 

78.       H. Ono, S. Shiori, and T. Sato

            "Parallactic Depth-Perception After Motion Adaptation"

            Invest. Ophthalmol. Vis. Sci. 32 (4), 1276-1276 (1991).

 

            ABSTRACT:

79.       K. Otsuka

            "Winner-Takes-All Dynamics And Antiphase States In Modulated Multimode Lasers"

            Phys. Rev. Lett. 67 (9), 1090-1093 (1991).

 

            ABSTRACT: (N - 1)! coexisting antiphase states are predicted to appear in an N-mode laser when the pump power drops below the threshold during part of the modulation cycle. The total output exhibits the so-called spiking mode pulsations at a frequency-omega-s. However, each longitudinal-mode output shows pulses at a frequency-omega-s/N, with each oscillator shifted by 2-pi/omega-s from its neighbor, resulting from a "winner-takes-all" dynamics. The assignment to antiphase states embedded in a high-dimensional phase space by injection seeding is shown. Applicability to a rewritable memory of (N - 1)! different "dynamical patterns" is demonstrated on the basis of numerical simulations.

 

80.       K. Otsuka

            "Self-Induced Path Formation Among Local Attractors And Spatiotemporal Chaos In A Complex Ginzburg-Landau Equation"

            Phys. Rev. A 44 (2), 1393-1396 (1991).

 

            ABSTRACT: Spatiotemporal behaviors involving coexisting attractors are investigated in discrete complex time-dependent Ginzburg-Landau equation systems. Complex dynamics connecting local attractors and an "attractor complex" born from destabilized coexisting equilibria are studied through numerical simulations. Majority-rule-based switching among two surviving attractors, inherent unstable motions reflecting the nature of the attractor complex, and "history-dependent" path formation resulting in the recovery of memory are shown in weakly coupled regimes. A relation with a continuum limit is briefly discussed.

 

81.       K. Otsuka

            "Complex Dynamics In Coupled Nonlinear Element Systems"

            Int. J. Mod. Phys. B 5 (8), 1179-1214 (1991).

 

            ABSTRACT: This paper reviews complex dynamics which arise through the interaction of simple nonlinear elements without chaotic response, including self-induced switching among local attractors (chaotic itinerancy) and related phenomena. Several realistic physical systems consisting of coupled nonlinear elements are considered on the basis of computer experiments: coupled nonlinear oscillator (e.g., discrete complex time-dependent Ginzburg-Landau equation) systems, coupled laser arrays, and a coupled multistable optical chain model.

 

82.       K. Otsuka

            "Chaotic Itinerancy In A Coupled-Element Multistable Optical Chain"

            Phys. Rev. A 43 (1), 618-621 (1991).

 

            ABSTRACT: Self-induced wandering among local attractors, that is, chaotic itinerancy, and the chaotic search of coexisting periodic or chaotic local orbits have been discovered in a nonequilibrium optical system with distributed nonlinear elements (Otsuka-Ikeda model system). It is shown on the basis of numerical simulations that spatiotemporal chaos in this system is interpreted as unstable motions which dynamically connect destabilized spatial structures via a chaotic itinerancy process.

 

83.       K. Otsuka and J. L. Chern

            "High-Speed Picosecond Pulse Generation In Semiconductor-Lasers With Incoherent Optical Feedback"

            Opt. Lett. 16 (22), 1759-1761 (1991).

 

            ABSTRACT: A novel method for producing high-speed picosecond optical pulses from semiconductor laser diodes that uses incoherent optical feedback is proposed. The incoherent optical feedback provides a successive pulselike modulation in carrier density and drives the system to a self-sustained pulsation state whose repetition rate is determined by relaxation oscillations.

 

84.       K. Otsuka, J. L. Chern, and J. K. McIver

            "Pitchfork Bifurcation And All-Optical Flip-Flop Operation With A Coupled Traveling-Wave Amplifier System"

            J. Opt. Soc. Am. B-Opt. Phys. 8 (6), 1304-1306 (1991).

 

            ABSTRACT: Mirrorless optical bistability arising through pitchfork bifurcation is predicted in a coupled anisotropic traveling-wave laser amplifier system. It is shown theoretically that an all-optical flip-flop operation can be attained by utilizing the complementary bistable characteristics of counterpropagating beams.

 

85.       C. Purcell, T. Mashiko, K. Odaka, and K. Ueno

            "Describing Head Shape With Surface Harmonic Expansions"

            IEEE Trans. Biomed. Eng. 38 (3), 303-306 (1991).

 

            ABSTRACT: Surface harmonic expansions are used to represent boundaries between regions of different conductivity in the human head. This facilitates calculation of the electric potential and magnetic field generated by neural current sources using discretized integral equations.

 

86.       S. Ramesh, N. Kobayashi, and Y. Horikoshi

            "Study Of High-Quality Znse/Gaas/Znse Single Quantum-Well And Znse/Gaas Heterostructures"

            J. Cryst. Growth 115 (1-4), 333-337 (1991).

 

            ABSTRACT: We have used the migration-enhanced epitaxy (MEE) technique to grow high-quality ZnSe/GaAs/ZnSe single quantum well (SQW) structures and ZnSe/GaAs heterostructures. The atomic layer controlled epitaxy of ZnSe-on-GaAs and the question of growth-rate/MEE cycle for ZnSe growth was also investigated. The first observation of luminescence from ZnSe/GaAs/ZnSe SQW structures is reported.

 

87.       S. Ramesh, N. Kobayashi, and Y. Horikoshi

            "High-Quality Znse/Gaas Superlattices - Mee Growth, And Structural And Optical Characterization"

            J. Cryst. Growth 111 (1-4), 752-756 (1991).

 

            ABSTRACT: High-quality ZnSe/GaAs superlattices were grown by migration-enhanced epitaxy (MEE) and characterized using X-ray diffraction, electron microscopy and photoluminescence. The streaky reflection high-energy electron diffraction (RHEED) pattern and strong, persistent RHEED oscillations observed during the MEE growth of the superlattices indicate a smooth growing surface. The sharp satellite peaks observed clearly in the double-crystal X-ray diffraction rocking curve of a 21-period ZnSe/GaAs superlattice confirm the excellent crystalline and interfacial quality of the superlattice. Cross-section transmission electron microscopy (TEM) shows flat, abrupt heterointerfaces. Superlattice photoluminescence spectra show that both photo-excited electrons and holes are confined in GaAs wells; also seen are the sharp excitonic features from the coherently strained ZnSe cap and barrier layers of the superlattice.

 

88.       T. S. Rao and Y. Horikoshi

            "Growth Of (Gaas)1-X(Si2)X Metastable Alloys Using Migration-Enhanced Epitaxy"

            J. Cryst. Growth 115 (1-4), 328-332 (1991).

 

            ABSTRACT: (GaAs)1-x(Si2)x for 0 < x < 0.25 has been successfully grown on GaAs (100) substrates using migration-enhanced epitaxy. Structural and compositional analysis of the as-grown (GaAs)1-x(Si2)x layers indicated single phase epitaxial crystals with zincblende structure in the compositional range 0 < x < 0.25. The lattice constant a0 of the alloys was found to decrease with increasing Si content from 0.56543 nm at x = 0 to 0.5601 nm at x = 0.25. Double-crystal X-ray diffraction rocking curve measurements and cross-sectional transmission electron microscopy studies carried out on a 10 period (GaAs)1-x(Si2)x/GaAs strained layer superlattice indicated sharp and abrupt interfaces of high crystalline quality.

 

89.       T. S. Rao, K. Nozawa, and Y. Horikoshi

            "Structural-Properties Of (Gaas)1-X(Si2)X Layers On Gaas(100) Substrates Grown By Migration-Enhanced Epitaxy"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (4A), L547-L550 (1991).

 

            ABSTRACT: Epitaxial (GaAs)1-x(Si2)x alloy layers (0 < x < 0.25) were grown on GaAs (100) substrates using Migration-Enhanced Epitaxy. Structural and compositional analysis of the as-grown (GaAs)1-x(Si2)x layers indicated single-crystal zincblende structure with no evidence of phase separation throughout the entire compositional range. The lattice constant a0 of the alloys was found to decrease linearly with increasing Si content from 0.56543 nm at x = 0 to 0.5601 nm at x = 0.25. Double crystal X-ray rocking curve measurements and cross-sectional transmission electron microscopy studies made on a 10 period (GaAs)0.80(Si2)0.20/GaAs strained-layer superlattice indicated sharp and abrupt interfaces of high crystalline quality.

 

90.       W. H. Richardson, S. Machida, and Y. Yamamoto

            "Squeezed Photon-Number Noise And Sub-Poissonian Electrical Partition Noise In A Semiconductor-Laser"

            Phys. Rev. Lett. 66 (22), 2867-2870 (1991).

 

            ABSTRACT: Amplitude noise on the light from a semiconductor laser produced a photocurrent fluctuation spectrum that was a maximum of 85% (-8.3 dB) below the shot-noise limit. Squeezing in semiconductor lasers is not limited by the overall quantum, or current transfer, efficiency from the laser injection current to the detector photocurrent. Current leakage away from the lasing junction does not introduce Poissonian partition noise.

 

91.       W. H. Richardson and Y. Yamamoto

            "Quantum Measurement Of The Photon Number Via The Junction Voltage In A Semiconductor-Laser"

            Phys. Rev. A 44 (11), 7702-7716 (1991).

 

            ABSTRACT: The quantum correlation between photon number and junction-voltage fluctuations in a constant-current-driven semiconductor laser is theoretically predicted and experimentally demonstrated. An external electrical circuit has the two functions of pumping to compensate for cavity loss and measuring the photon number. The photon-number noise can be reduced to below the standard quantum limit and even to near that of a number state by referring to the junction-voltage measurements. Phase diffusion incorporates the inherent back action noise of such a measurement process. The number-phase uncertainty principle is conserved between the measurement-induced sub-Poissonian photon-number noise and the Schawlow-Townes phase-diffusion noise.

 

92.       W. H. Richardson and Y. Yamamoto

            "Quantum Correlation Between The Junction-Voltage Fluctuation And The Photon-Number Fluctuation In A Semiconductor-Laser"

            Phys. Rev. Lett. 66 (15), 1963-1966 (1991).

 

            ABSTRACT: The photon-number fluctuation of the external field from a semiconductor laser-which was reduced to below the standard quantum limit-is shown to be correlated with the measured junction-voltage noise. The spectral density of the sum of the photon-number fluctuation and junction-voltage fluctuation falls below the squeezed photon-number fluctuation. This confirms the theoretical predictions that this correlation, which originates in the dipole interaction between the internal field and electron-hole pairs, extends into the quantum regime.

 

93.       K. Saito, S. Yamada, A. Ohki, and K. Ando

            "Analysis Of Donor And Compensation Ratio In I-Doped Znse By Far-Infrared Magnetoabsorption"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (1B), L74-L77 (1991).

 

            ABSTRACT: The first far-infrared (FIR) magnetoabsorption study of iodine (I)-doped n-ZnSe is described. The FIR experiments are carried out by observing the Zeeman absorption spectra with a FIR-laser and high-magnetic fields. Four different donor species, including the I-donor, are resolved, and the I-donor ionization energy of 25.6 meV is precisely estimated. Moreover, compensation ratios and absolute donor (or acceptor) densities N(d) are determined. As a result, it is found that the acceptor density N(a) increased almost linerly with increasing N(d). This suggests a deep and complex origin for the acceptors in the I-doped ZnSe.

 

94.       J. Sakai and E. A. J. Marcatili

            "Lossless Dielectric Tapers With 3-Dimensional Geometry"

            J. Lightwave Technol. 9 (3), 386-393 (1991).

 

            ABSTRACT: General properties of two-dimensional tapers for the cylindrical coordinate systems are described. A criterion to determine the index distribution of lossless tapers is given in terms of the phase shift. Next, the design method of lossless tapers with three-dimensional geometry is presented. After design equations of tapers are described for spherical, conical, and ellipsoidal coordinate systems, some specific design examples are presented. It is shown that equations for the ellipsoidal coordinates can be reduced to those for coordinate systems having high symmetry.

 

95.       T. Saku, Y. Hirayama, and Y. Horikoshi

            "High Electron-Mobility In Algaas/Gaas Modulation-Doped Structures"

            Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 30 (5), 902-905 (1991).

 

            ABSTRACT: AlGaAs/GaAs modulation-doped structures with low-temperature electron mobility exceeding 10(7) cm2/Vs at a carrier concentration of 2.5 approximately 3 x 10(11) cm-2 are grown by molecular beam epitaxy. Electron mobility above 8 x 10(6) cm2/Vs is reproducibly obtained over more than 6 months by careful baking of the growth system and optimization of the layer structure. Voltage-current measurements showing nonlinear and negative resistance characteristics at low temperatures indicate that the ballistic motion of electrons dominates the transport characteristics of these samples.

 

96.       N. Sarukura, Y. Ishida, and H. Nakano

            "Generation Of 50-Fsec Pulses From A Pulse-Compressed, Cw, Passively Mode-Locked Ti-Sapphire Laser"

            Opt. Lett. 16 (3), 153-155 (1991).

 

            ABSTRACT: Stable pulses of less than 150 fsec are generated directly from a tunable cw passively mode-locked Ti:sapphire laser, through a balance of salf-phase modulation in the Ti:sapphire rod and negative group-velocity dispersion produced by a prism pair. After external fiber compression, 50-fsec pulses are obtained at approximately 750 nm.

 

97.       S. Sasaki, K. Kinoshita, and A. Matsuda

            "Nuclear-Resonance Study Of Superconducting La1.82ca1.18cu2o6"

            Physica C 185, 1083-1084 (1991).

 

            ABSTRACT: By high oxygen pressure synthesis, La1.82Ca1.18Cu2O6 was found to be superconducting (T(C)(zero) = 49K). Using the conventional spin-echo method, a nuclear resonance experiment is conducted on a powder La1.82Ca1.18Cu2O6 sample. Nuclear Quadrupole Resonance (NQR) spectrum of La-139 at 4.2K is obtained for the first time. The quadrupolar frequency (nu-Q) was estimated to be 5.9 +/- 0.1 MHz. The broad spectrum (the full width at half maximum intensity is about 2.5MHz) indicates that the electric field gradient (EFG) is distributed. Spin-lattice relaxation time (T1) is also discussed.

 

98.       M. Sato and Y. Horikoshi

            "Effect Of Indium Replacement By Gallium On The Energy Gaps Of Inas/Gaas Thin-Layer Structures"

            J. Appl. Phys. 69 (11), 7697-7702 (1991).

 

            ABSTRACT: Energy gaps of InAs/GaAs thin-layer structures are calculated using a modified finite square well model, which takes into account In-Ga replacement during growth. We compare the calculated results with the experimental energy gaps of structures grown by flow-rate modulation epitaxy, which is based on an alternate supply of gaseous sources, and molecular-beam epitaxy. The results indicate that In-Ga replacement is rare in flow-rate modulation epitaxy, but about 90% of the surface In atoms are replaced with the Ga atoms in molecular-beam epitaxy. Arsenic has a low sticking coefficient on the In surface, so it is difficult to achieve high As coverages on the In surface in molecular-beam epitaxy. In flow-rate modulation epitaxy and metalorganic chemical vapor deposition, the dangling bonds of the surface As atoms are probably terminated by hydrogen atoms. The surface As atoms are stabilized by establishing stable sp3 orbitals and prevent In-Ga replacement.

 

99.       M. Sato, N. Kobayashi, and Y. Horikoshi

            "Effect Of Precracking Of Organometallics And Arsine On Growth Of Gaas"

            J. Cryst. Growth 115 (1-4), 221-225 (1991).

 

            ABSTRACT: We present a new growth apparatus used to achieve the low temperature growth of high-quality epitaxial layers through the controlled decomposition process of group-III organometallics and group-V hydrides, which are independent of the substrate temperature. Cracking cells for both sources are installed in a chamber. The effect of precracking of organometallics is investigated for the first time. GaAs layers were successfully grown using trimethylgallium and arsine at a low substrate temperature (500-degrees-C) and at very low reactor pressure (10-20 Pa). When arsine was precracked, specular surfaces were obtained at a very small As/Ga ratio of 3.5. Precracking of trimethylgallium drastically reduced the carbon concentration of GaAs from 10(20) to 10(18) cm-3. Further decreases in carbon concentration, down to 10(17) cm-3, were achieved by increasing the As/Ga ratio to 10. Our results indicate that the decomposition process of trimethylgallium can be controlled, supplying Ga atoms to the substrate surface.

 

100.    M. Sato and M. Weyers

            "Adsorption And Decomposition Of Organometallics On Gaas-Surfaces In Low-Pressure Metalorganic Chemical Vapor-Deposition"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (11B), L1911-L1913 (1991).

 

            ABSTRACT: To determine the mechanism of surface reactions during metalorganic chemical vapor deposition, we perform mass spectrometric studies of the products desorbed from a GaAs surface upon pulsed supply of the reactants. We find that the surface after trimethylgallium (TMG) exposure is terminated by CH3 and that the desorption of the CH3 from the surface is activated by the presence of As. The adsorption of triethylgallium (TEG) is inhibited on a CH3-terminated surface whereas TEG is decomposed both on As-rich and on Ga-rich surfaces. The effect of CH3 termination is highlighted by the complete inhibition of triethylaluminum decomposition when it is introduced together with TMG.

 

101.    T. Sato

            "Stimulus Parameters Underlying The Short-Range And Long-Range Difference"

            Invest. Ophthalmol. Vis. Sci. 32 (4), 826-826 (1991).

 

            ABSTRACT:

102.    W. P. Schleich, J. P. Dowling, and R. J. Horowicz

            "Exponential Decrease In Phase Uncertainty"

            Phys. Rev. A 44 (5), 3365-3368 (1991).

 

            ABSTRACT: The phase probability curve of a recently proposed photon state consists of a broad background with a sharp central peak [J. H. Shapiro, S. R. Shepard, and N. Wong, Phys. Rev. Lett. 62, 2377 (1989)]. These authors argue that the inverse peak-height phase uncertainty delta-phi of this distribution decreases inversely as the square of the mean photon number <m>-an improvement over either coherent or highly squeezed states. We show that the width DELTA-phi of the best-fitting Gaussian to the central peak-a measure of phase uncertainty tailored to this narrow feature-decreases exponentially with increasing <m>. The importance of this result may be offset by the observation that the area under this peak also vanishes very rapidly.

 

103.    K. Semba, T. Ishii, and A. Matsuda

            "Study Of Superconducting Fluctuation Using Yba2cu3o7 Single-Crystals"

            Physica C 185, 1303-1304 (1991).

 

            ABSTRACT: In normal-state magnetoresistance studies, the layered structure and short coherence length of high-T(C) superconductors make it possible to observe the Zeeman effect on superconducting fluctuation. Two problems, however, remain: (1) the Zeeman effect on the Maki-Thompson fluctuation (MTZ) in the Aronov-Hikami-Larkin (AHL) theory, and (2) whether the the clean or dirty limit approximation is valid. We have therefore studied the magnetoresistance of YBa2Cu3O7 bulk single crystals. We experimentally demonstrate that the MTZ fluctuation as presented in the AHL theory are absent. Moreover, we find that clean limit analysis without the MTZ component (ALO+MTO+ALZ) closely fits the experimental data. We obtained results quantitatively consistent with the results of recent optical and transport studies using YBa2Cu3O7 single crystals.

 

104.    K. Semba, T. Ishii, and A. Matsuda

            "Absence Of The Zeeman Effect On The Maki-Thompson Fluctuation In Magnetoresistance Of Yba2cu3o7 Single-Crystals"

            Phys. Rev. Lett. 67 (6), 769-772 (1991).

 

            ABSTRACT: We experimentally demonstrated the absence of the Zeeman effect on the Maki-Thompson fluctuation (MZT) in the Aronov-Hikami-Larkin theory. Moreover, we find that clean-limit analysis without the MTZ component closely fits the experimental data. Our analysis provides a quantitatively consistent picture of Y-Ba-Cu-O including transport and optical studies.

 

105.    N. Shigekawa and E. Yamaguchi

            "A Monte-Carlo Supercell Approach For The Effects Of Disorder On The Upper-Valley Electronic-Properties In Ingaas Ternary Alloys"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (8A), L1340-L1342 (1991).

 

            ABSTRACT: We propose a novel approach (Monte Carlo supercell approach) for investigating the effects of disorder on the upper-valley electronic properties in an InGaAs ternary alloy. In this approach, the electronic properties in supercells with random atomic configurations are analyzed using the sp3s* tight-binding method. Effects of the bond-length difference in the alloy are considered in the present analysis. The effects of disorder on the upper-valley electronic properties have been evaluated by examining the spectral function. The disorder-limited upper-valley electron relaxation time obtained from the spectral function is much shorter than that due to the intervalley-phonon scattering, which indicates that the disorder in the InGaAs alloy induces strong effects on the electron transport properties in high electric fields.

 

106.    S. Shioiri, H. Ono, and T. Sato

            "Adaptation Of Relative Motion Detectors"

            Invest. Ophthalmol. Vis. Sci. 32 (4), 827-827 (1991).

 

            ABSTRACT:

107.    A. Sugimura

            "Effect Of Scattering In Electrodes On Double-Barrier Resonant Tunneling"

            Phys. Rev. B 43 (5), 4276-4285 (1991).

 

            ABSTRACT: Assuming that electrons in quantum-well and electrode regions are well separated from each other, resonant tunneling is analyzed as a quantum transition from one electrode to the other, in which the effects of scattering in the electrodes are introduced through damping constants. Explicit formulas for tunneling currents are obtained for long- and short-electrode limits. It is found, for the long-electrode case, that a coherent tunneling process predominates over an incoherent process when the damping constant gamma-12 for the current operator is smaller than the electron transfer rate through a barrier, while the incoherent process dominates when gamma-12 is larger. It is also found that there is a quantum-transition region near the barrier inside the electrode, where the carrier density and the local current are not homogeneous. The coherent interaction length, defined as the size of the quantum-transition region, is a monotonic decreasing function with respect to the damping constant. In the short-electrode limit too, there is a quantum-transition region. The tunneling current in this region is linearly dependent on the electrode size.

 

108.    M. Suzuki and T. Fukuda

            "Scanning-Tunneling-Microscopy Observation Of Aluminum On Gaas(110) Surfaces"

            Phys. Rev. B 44 (7), 3187-3190 (1991).

 

            ABSTRACT: The surface structure of aluminum overlayers on cleaved p-type GaAs (110) is studied by scanning tunneling microscopy (STM) in ultrahigh vacuum. About three monolayers of aluminum were deposited on the surfaces at room temperature. We observed that aluminum atoms form clusters, and found that one cluster, consisting of about 200 atoms, has nonmetallic characteristics with a band gap of 1 eV. We also observed adsorbed atoms located over Ga sites in STM images of both occupied and unoccupied states. Their corrugation amplitudes are about 1 angstrom above the GaAs surface.

 

109.    A. Taguchi, H. Nakagome, and K. Takahei

            "Thermal Quenching Mechanism Of Yb Intra-4f-Shell Luminescence In Inp"

            J. Appl. Phys. 70 (10), 5604-5607 (1991).

 

            ABSTRACT: Thermal quenching mechanism of Yb intra-4f-shell luminescence were clarified by studying the temperature dependences of electrical and optical properties of Yb-doped InP samples. The quenching mechanism which depends on shallow donor concentration was found by comparing temperature dependences of Yb 4f-shell luminescence and free-carrier concentration. This mechanism is a localized Auger effect and is efficient below about 70 K in samples having a larger donor concentration than Yb concentration. At higher temperatures, another quenching mechanism was found to be efficient which does not depend on donor concentration. This quenching of Yb intra-4f-shell luminescence is accompanied by some increase of band-edge related luminescence. This phenomenon is explained by the energy back-transfer mechanism from the excited Yb 4f-shell to the InP host. Although an importance of the free-carrier Auger effect has been suggested in conducting materials, we propose that above two mechanisms dominate the quenching of the Yb 4f-shell luminescence in InP.

 

110.    T. Takagahara

            "Dependence On Dimensionality Of Excitonic Optical Nonlinearity In Quantum Confined Structures"

            Solid State Commun. 78 (4), 279-282 (1991).

 

            ABSTRACT: The dependence on dimensionality of the excitonic optical nonlinearity and the figures of merit in quantum confined structures is clarified for the resonant third-order optical nonlinearity. An important parameter which determines the dimensionality dependence of the figures of merit is found to be the ratio of the homogeneous linewidth to the exciton binding energy or the ratio of the exciton coherence length to the exciton Bohr radius. It is predicted that for the III-V compound semiconductors the exciton confinement in low-dimensional structures (d = 1,2 d:dimensionality) is favorable for enhancing the figures of merit, whereas for the I-VII compound semiconductors the exciton confinement does not always improve the figures of merit.

 

111.    H. Takayanagi, K. Inoue, and Y. Tanaka

            "Local Tunneling Spectroscopy Of The Quasi-Particle In A Nb/Inas/Nb System"

            Physica B 169 (1-4), 467-468 (1991).

 

            ABSTRACT: Local tunneling spectroscopy for a Nb/InAs/Nb superconducting proximity effect system was accomplished with an STM at 4.2 K. The measured tunneling conductance showed spatial dependence in the InAs region. The local DOS of the bound states for this system was obtained using Green's function. The tunneling conductance calculated with this local DOS reproduced the experimental results well. The data and calculations suggest the existence of bound states with spatially dependent local DOS in the InAs region, where a finite value for the pair potential is induced by the proximity effect.

 

112.    K. Takei and Y. Maeda

            "Nmr-Study Of Compositional Inhomogeneities In Sputtered Co-Cr Films"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (6B), L1125-L1128 (1991).

 

            ABSTRACT: The development of compositional inhomogeneities in sputtered Co-22 at.% Cr films is studied as a function of substrate temperature using the spin-echo Co-59-NMR technique. It is observed that a highly Co-rich component grows as the substrate temperature increases from 30-degrees-C to 400-degrees-C. The Cr content of the Co-rich part in the film deposited at 400-degrees-C is estimated to be as low as 5-7 at.%. The results are consistent with the appearance of a clearly striped compositional microstructure which suggests compositional separation.

 

113.    M. Taniguchi, H. Nakagome, and K. Takahei

            "Observation Of Luminescence From A Highly Concentrated Nd Center In Gap By Direct Optical-Excitation And Comparison With Nd Centers Excited Under Host Excitation"

            Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 30 (12B), 3788-3791 (1991).

 

            ABSTRACT: We report the studies of direct excitation on Nd-doped GaP samples grown by metalorganic chemical vapor deposition. It is found that extremely sharp photoluminescence excitation lines, with full width at half maximum of less than 0.02 nm at 4 K, can be observed when the excitation photon energy is in resonance with the Nd internal 4f-shell transition energy. We used direct excitation spectra to estimate the concentration of each individual Nd luminescence center, and found that the majority of the Nd ions form one particular kind of noncubic center which cannot be effectively excited through energy transfer from the host crystal. Such a phenomenon is likely to be the reason why the efficiencies of the rare-earth-doped III-V compounds are low. It also suggests that if we can fully utilize all the available rare-earth ions, a much higher efficiency can be achieved.

 

114.    M. Taniguchi, H. Nakagome, and K. Takahei

            "Luminescence Intensity And Lifetime Dependences On Temperature For Nd-Doped Gap And Gaas"

            Appl. Phys. Lett. 58 (25), 2930-2932 (1991).

 

            ABSTRACT: We report the studies of luminescence intensity and lifetime dependences on temperature for Nd-doped GaP and GaAs samples grown by metalorganic chemical vapor deposition. It is found that, with above band-gap excitation, the temperature dependence of GaP:Nd reveals a two-step decreasing behavior as the sample temperature increases. This phenomenon is due to the fact that there exist two kinds of Nd centers (type I and type II) in GaP. Although type I Nd centers produce strong luminescence at low temperatures, their intensities drop rapidly above 40 K. On the other hand, type Il Nd centers show a near constant intensity up to 150 K and can still be observed up to room temperature. We also found, for a given Nd center, that the luminescence lifetime dependence on temperature is identical to the temperature quenching behavior of luminescence intensity. From the similarity between the quenching behaviors of Nd-related luminescence intensities and lifetimes, we conclude that the temperature quenching of luminescence intensity of these Nd-doped GaP and GaAs samples is mainly due to deexcitation rather than the reduction of excitation efficiency.

 

115.    S. Tarucha and Y. Hirayama

            "Magnetotunneling In A Coupled 2-Dimensional One-Dimensional Electron-System"

            Phys. Rev. B 43 (11), 9373-9376 (1991).

 

            ABSTRACT: Magnetotunneling in a double-barrier diode with a restricted lateral dimension was studied. The zero-field tunneling current shows fine structures supposed to be due to mixing of two-dimensional emitter subbands with one-dimensional subbands in the double-barrier region. Application of a magnetic field causes a depopulation of the current structure. This arises from couplings of electromagnetic subbands with and without conservation of the quantum numbers.

 

116.    S. Tarucha, Y. Hirayama, and Y. Tokura

            "Resonant Tunneling Through One-Dimensional States Constricted By Alxga1-Xas/Gaas/Alxga1-Xas Heterojunctions And High-Resistance Regions Induced By Focused Ga Ion-Beam Implantation"

            Superlattices Microstruct. 9 (3), 341-344 (1991).

 

            ABSTRACT:

117.    S. Tarucha, Y. Hirayama, and Y. Tokura

            "Subband Mixing Effect In Double-Barrier Diodes With A Restricted Lateral Dimension"

            Appl. Phys. Lett. 58 (15), 1623-1625 (1991).

 

            ABSTRACT: Tunneling characteristics of double-barrier diodes with a restricted lateral dimension are studied. When a large number of closely spaced emitter subbands contribute to the tunneling, the current versus voltage characteristics exhibit a series of peaks separated by the voltages that correspond to subband splittings in the double-barrier region. When the lowest emitter subband mainly contributes to the tunneling, they exhibit peaks separated by approximately twice the voltages that correspond to the subband splittings in the double-barrier region. These differences can be explained by the effects of mixing two-dimensional emitter subbands with one-dimensional subbands in the double-barrier region.

 

118.    S. Tarucha, Y. Tokura, and Y. Hirayama

            "Resonant Tunneling Of 3-Dimensional Electrons Into Degenerate Zero-Dimensional Levels"

            Phys. Rev. B 44 (24), 13815-13818 (1991).

 

            ABSTRACT: A series of current peaks is observed at the onset of tunneling current in three-dimensionally confined tunneling diodes. The respective neighboring current peaks have an equivalent amplitude difference, which is independent of the diode lateral size. We interpret these peaks as being due to the tunneling of a three-dimensional emitter electron at the Fermi energy through the zero-dimensional well levels. The peak current is defined by the degeneracy of the zero-dimensional level confined by a harmonic lateral potential.

 

119.    T. J. Thornton, S. Yamada, M. Yamamoto, and K. Aihara

            "Current Voltage Characteristics Of Bend In Mesoscopic Wire"

            Electron. Lett. 27 (13), 1177-1178 (1991).

 

            ABSTRACT: The four terminal resistance of a bend in a mesoscopic wire changes sign with increasing temperature. This transition leads to a nonlinear I/V characteristic which can, under suitable bias conditions, be used to produce frequency doubling.

 

120.    C. Tombling, T. Saitoh, Y. Suzuki, and H. Tanaka

            "Experimental Gain And Saturation Performance Of Gaas/Algaas Sch Quantum-Well Traveling-Wave Optical Amplifier"

            Electron. Lett. 27 (15), 1374-1376 (1991).

 

            ABSTRACT: Successful combination of high gain and high saturation output power performance in a GaAs/AlGaAs quantum well travelling wave amplifier is reported. Comparable performance to similar 1.5-mu-m InGaAs/InP devices is achieved, surpassing expectations. A device with a three quantum well active region and separately confined heterostructure design has both a small signal gain of 22.9 dB and a saturation output power of 40 mW at the low drive current of 40 mA.

 

121.    Y. Tomioka, Y. Nakayama, M. Naito, T. Matsushita, I. Tanaka, H. Kojima, T. Ishii, K. Kishio, K. Yamafuji, and K. Kitazawa

            "Quantitative-Analysis Of Zero-Field Cooling And Field Cooling Curves To Determine The Critical Current-Density And Lower Critical-Field"

            Physica C 185, 2163-2164 (1991).

 

            ABSTRACT: Field-cooled (FC) and zero-field-cooled (ZFC) magnetization curves were measured for the single crystals of YBa2Cu3O7 and (La1-xSrx)2CuO4 (x = 0.065) under several magnetic fields. Using the extended Bean's critical state model, J(c) and lower critical field H(c1)(0) were estimated as fitting parameters to explain FC and ZFC curves consistently. The J(c)(T) values thus obtained well agreed with the reported ones obtained by the other method.

 

122.    K. Tsubaki, T. Honda, H. Saito, and T. Fukui

            "Electron Wave Interference Device With Fractional Layer Superlattices"

            Appl. Phys. Lett. 58 (4), 376-378 (1991).

 

            ABSTRACT: Modulation-doped Al0.3Ga0.7As/GaAs heterostructure electron wave interference devices with fractional layer superlattices are fabricated. The periods of the fractional layer superlattices in the electron wave interference devices are 16, 12, and 8 nm, respectively. These devices show drain current oscillation due to electron wave interference at 4.2 K. The oscillation periods is determined by the period of the fractional layer superlattice. From the analysis of the drain current oscillation, the peaks of the structure function agree with the multiples of the periods of the fractional layer superlattice.

 

123.    M. Ueda and N. Hatakenaka

            "Theory Of Mesoscopic Tunnel-Junctions - From Shot Noise To The Standard Quantum Limit"

            Phys. Rev. B 43 (6), 4975-4987 (1991).

 

            ABSTRACT: We predict two distinct types of crossovers and fundamental quantum-noise limits that single-electron-tunneling (SET) statistics in an ultrasmall normal tunnel junction will exhibit as external macroscopic conditions are changed. When the product of source voltage V and electrostatic capacitance C of the junction is given, SET events exhibit a crossover from random shot noise to Coulomb-regulated oscillations as the ratio of source-to-tunnel resistance R(S)/R(T) becomes larger. This regularity, however, has a fundamental upper bound, which we refer to as the standard quantum limit. It is shown that the standard quantum limit does not originate from the current or from thermal fluctuations but originates from the time-energy uncertainty principle that is inherent in quantum-mechanical tunneling. In particular, the time-energy uncertainty relationship is derived that is unique to single-electron tunneling by Coulomb blockade. On the other hand, when the ratio of source-to-tunnel resistance R(S)/R(T), is given, it is found that the degree of randomness of SET oscillations decreases as the product CV reduces to an optimum value above e/2, but that it rapidly increases as the product further reduces towards e/2. Such an optimum value is shown to emerge as a balancing point between an ordering force (arising from Coulomb blockade) and a fluctuating force (caused by quantum-mechanical tunneling). The optimum value is numerically evaluated over a wide range of the ratio R(S)/R(T). The whole analysis in the present paper employs a semiclassical model but it is based on an exact, analytic methodology. By so doing, a critical point is reached where the semiclassical theory of Coulomb blockade manifestly breaks down.

 

124.    K. Uwai

            "Sequential Self-Limiting Growth Of Cuo On Mgo(100) By Chemical Vapor-Deposition"

            J. Cryst. Growth 112 (1), 298-301 (1991).

 

            ABSTRACT: Sequential self-limiting growth by chemical vapor deposition is demonstrated for CuO(111) on MgO(100) for the first time by supplying CuCl and O2/H2O alternately. When the CuCl supply duration in a growth cycle is increased, the grown thickness per cycle saturates at 2.0-2.2 angstrom, which is close to the monolayer thickness of CuO (2.32 angstrom) in the [111] direction. This suggests that near monolayer growth occurs in each supply cycle by the self-limiting growth mechanism.

 

125.    T. Watanabe, T. Ishii, K. Kinoshita, and A. Matsuda

            "Growth And Anisotropic Properties Of Superconducting La2-Xca1+Xcu2o6-X/2+Delta Single-Crystals"

            Physica C 185, 1235-1236 (1991).

 

            ABSTRACT: Single crystals of La2-xCa1+xCu2O6-x/2+delta have been grown by the CuO flux method. After annealing under a high partial pressure of O2, these crystals showed zero resistance at 41 K and a perfect shielding effect (3% Meissner signal). These crystals also showed metallic behaviour parallel (a,b) and perpendicular (c) to the basal plane, with an anisotropy of about 30 at room temperature. The Ginzburg-Landau coherence lengths were estimated from Hc2 measurements: xi-ab = 33 angstrom and xi-c = 12 angstrom. The anisotropy factor of 3 is fairly small for a high-Tc superconductor.

 

126.    T. Watanabe and A. Matsuda

            "Anisotropic Conductivity And Its Anomalies In La8-Xsrxcu8o20 Single-Crystals"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (6A), L985-L987 (1991).

 

            ABSTRACT: Single crystals of La(8-x)Sr(x)Cu8O20 (1.0 less-than-or-equal-to x less-than-or-equal-to 1.8) are grown using the CuO flux method in a flowing O2 atmosphere. Resistivities parallel to the c-axis, rho parallel-to c, and perpendicular to the c-axis, rho perpendicular-to c, each show an anomaly around 140 K. The anisotropy rho perpendicular-to c/rho parallel-to c increases from 5 approximately 10 at room temperature to 8 approximately 20 at 5 K. These La(8-x)Sr(x)Cu8O20 crystals can be considered quasi-one-dimensional conductors. Magnetic susceptibilities for both H parallel-to c and H perpendicular-to c show a cusplike anomaly around 140 K, suggesting the occurrence of a magnetic phase transition.

 

127.    M. Weyers and M. Sato

            "Growth Of Gap By Movpe At Very Low-Pressure - Kinetics And Carbon Incorporation"

            J. Cryst. Growth 115 (1-4), 469-473 (1991).

 

            ABSTRACT: GaP is grown from TMG and precracked phosphine at 15 Pa. At this pressure, prereactions in the gas phase are suppressed and growth is governed by surface reactions, as in MOMBE. These surface reactions kinetically limit the TMG decomposition up to 640-degrees-C. Additionally, there is a strong dependence on the P supply leading to lower rates at higher P fluxes. This decrease is attributed to a blocking of the surface by P species leading to a suppression of the adsorption of TMG. Besides this, the carbon concentration in the films is reduced at increased P flux. Both effects are most pronounced at higher growth temperature (640-degrees-C). At the highest carbon concentrations obtained in this study ([C] = 1.1 x 10(21) cm-3), analysis of the lattice constant reveals a lattice contraction smaller than expected, suggesting an incorporation of carbon both on lattice and interstitial sites. Such incorporation behaviour leads to a low level of electrical activation as acceptor.

 

128.    K. Winer

            "Defects In Hydrogenated Amorphous-Silicon"

            Annu. Rev. Mater. Sci. 21, 1-21 (1991).

 

            ABSTRACT:

129.    K. Winer, M. Kawashima, and Y. Horikoshi

            "Si Doping Efficiency In Gaas Grown At Low-Temperatures"

            Appl. Phys. Lett. 58 (24), 2818-2820 (1991).

 

            ABSTRACT: The doping efficiency of Si (= [e-]/[Si]) has been measured as a function of substrate temperature T(s), beam-equivalent As4-to-Ga fluence ratio R, and beam supply conditions to probe the kinetic limitations of low-temperature GaAs homoepitaxy. The doping efficiency decreases strongly with increasing R at low T(s) due, we suggest, to electron trapping at defects caused by excess As incorporation.

 

130.    W. H. Xiang, S. R. Friberg, K. Watanabe, S. Machida, W. B. Jiang, H. Iwamura, and Y. Yamamoto

            "Femtosecond External-Cavity Surface-Emitting Ingaas Inp Multiple-Quantum-Well Laser"

            Opt. Lett. 16 (18), 1394-1396 (1991).

 

            ABSTRACT: We demonstrate that a synchronously pumped In0.53Ga0.47As/InP multiple-quantum-well surface-emitting laser in an external cavity can produce 36-ps pulses with a high average power of 260 mW and a broad spectral width of 18 nm. The output pulses are strongly upchirped and could be shortened to 153 fs with peak powers exceeding 1 kW by chirp compensation with a diffraction grating pair.

 

131.    W. H. Xiang, S. R. Friberg, K. Watanabe, S. Machida, Y. Sakai, H. Iwamura, and Y. Yamamoto

            "Sub-100 Femtosecond Pulses From An External-Cavity Surface-Emitting Ingaas/Inp Multiple Quantum-Well Laser With Soliton-Effect Compression"

            Appl. Phys. Lett. 59 (17), 2076-2078 (1991).

 

            ABSTRACT: We have compressed strongly chirped optical pulses from a synchronously pumped In0.53Ga0.47As/InP multiple quantum well surface-emitting laser operating with an external cavity. The pulses, initially exhibiting a strong up-chirp with a time-bandwidth product of more than 100 times the Fourier transform limit, were compressed to 77 fs using dispersion and soliton compression in a negative group-velocity-dispersion fiber. Chirp compensation using a diffraction grating pair followed by soliton compression in a fiber gave pulses as short as 21 fs.

 

132.    W. H. Xiang, W. B. Jiang, and Y. Z. Ishida

            "Femtosecond Pulses Generated From Non-Colliding Pulse Mode-Locked Ring Dye-Lasers"

            Opt. Commun. 86 (1), 70-74 (1991).

 

            ABSTRACT: Optical pulses shorter than 50 fs have been directly generated from non-colliding pulse mode-locked ring dye lasers with a four-prism sequence. This result supports the view that the balance between the self-phase modulation and the group velocity dispersion inside the cavity, and the greater flexibility of the ring cavity over the standing wave cavity, are the main factors in obtaining femtosecond pulses from the colliding pulse mode-locked ring dye lasers.

 

133.    S. Yamada and M. Yamamoto

            "Quantum Oscillation Of Transverse Resistance And Resistance Reciprocity As A Point-Contact Boundary-Problem"

            Phys. Rev. B 43 (11), 9369-9372 (1991).

 

            ABSTRACT: Transverse resistance has been investigated in a small cross with two point contacts (PC's) as a PC boundary problem. The sample structure can be considered as a series of PC's or as a quasiballistic wire defined by the opposite PC boundaries. Transverse-resistance oscillations in phase with longitudinal-resistance plateaus were observed at equilibrium conditions. The oscillation and the plateau appeared invariably, even when the terminals for current flow and transverse voltage probing were exchanged, suggesting "reciprocities" originating from the PC boundaries. These results also demonstrate that the longitudinal resistance of the quasiballistic wire reveals quantized plateaus, if it has opposite PC boundaries. These reciprocities are discussed with reference to a global symmetry rule of resistance. The origin of the transverse-resistance oscillation is also discussed.

 

134.    Y. Yamada, K. Kinoshita, T. Matsumoto, F. Izumi, and T. Yamada

            "Pressure Effects On Tc Of Superconducting La2-Xca1+Xcu2o6"

            Physica C 185, 1299-1300 (1991).

 

            ABSTRACT: The superconducting transition temperature T(c) was measured as a function of pressure (P) up to 2 GPa for Ca-based 2-1-2-6 compounds, La2-xCa1+xCu2O6 (0.15 less-than-or-equal-to x less-than-or-equal-to 0.25). The T(c)'s of these compounds were weakly dependent on pressure. The pressure coefficients of T(c) changed sign from positive to negative with increasing pressure at P almost-equal-to 1 GPa for each composition studied. The results can be explained by only small changes of hole concentration in this pressure region.

 

135.    E. Yamaguchi, K. Shiraishi, and T. Ohno

            "1st Principle Calculation Of The Dx-Center Ground-States In Gaas, Alxga1-Xas Alloys And Alas/Gaas Superlattices"

            J. Phys. Soc. Jpn. 60 (9), 3093-3107 (1991).

 

            ABSTRACT: The atomistic nature of the deep donor levels referred to as DX centers in GaAs, AlxGa1-xAs alloys and AlAs/GaAs superlattices is investigated by applying the ab initio self-consistent pseudopotential method to 64-atom super cells. The total energy and force calculations reveal that the most stable state is the T(d)-distorted atomic configuration around a substitutional donor with the neighbouring bond relaxation given by the effective ionic radius (0.7% for Si(Ga)). On the contrary, a negatively charged donor with broken-bond configuration is shown to give a metastable state and not the ground state even under high hydrostatic pressures. It is found that a deep A1 level attributable to the DX center is induced by a simple substitutional donor with the obtained optimal lattice configuration. The theory successfully explains experimental results on the thermal and optical ionization energies for the DX centers.

 

136.    H. Yamaguchi and Y. Horikoshi

            "Influence Of Surface Reconstruction On The As Desorption Process From A (001) Gaas Surface Evaluated By Improved High-Energy Electron-Reflectivity Measurements"

            Phys. Rev. B 44 (11), 5897-5900 (1991).

 

            ABSTRACT: Electron-beam specular reflectivity in high-energy electron diffraction is evaluated quantitatively by measuring the reflected electron-beam current. Using this method, As desorption from a (001) GaAs surface is studied in detail. This desorption process is sensitive to the transition of surface reconstruction and the activation energy for this process changes according to the reconstruction transition.

 

137.    H. Yamaguchi and Y. Horikoshi

            "Influence Of An As-Free Atmosphere In Migration-Enhanced Epitaxy On Step-Flow Growth"

            Jpn. J. Appl. Phys. Part 1 - Regul. Pap. Short Notes Rev. Pap. 30 (4), 802-808 (1991).

 

            ABSTRACT: Reflection high-energy electron diffraction is observed during the growth of GaAs, AlGaAs, and InAs by migration-enhanced epitaxy on misoriented (100) substrates. The influence of an As-free atmosphere during Ga deposition in migration-enhanced epitaxy on step-flow growth is examined. Measurements of the change in specular peak intensity show that an As-free atmosphere accelerates step-flow growth, and that the ease with which step-flow growth occurs follows the order of InAs, GaAs, and AlGaAs. On the other hand, measurements of the specular peak width of the diffraction intensity profiles show that uniform step structures can be obtained for GaAs and AlGaAs layers under the same conditions if a small amount of As pressure is added during the metallic atom deposition in the process of migration-enhanced epitaxy.

 

138.    Y. Yamamoto and G. Bjork

            "Lasers Without Inversion In Microcavities"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (12A), L2039-L2041 (1991).

 

            ABSTRACT: The lasing characteristics of microcavity lasers with high coupling efficiency of spontaneous emission into the lasing mode are studied. Output power, population inversion, spectral linewidth and intensity noise are calculated as functions of pumping rate. When the spontaneous emission coupling efficiency into the lasing mode is close to one, a lasing threshold characterized by a sharp increase in an output power, a clamping of population inversion, a decrease in spectral linewidth and a peak in intensity noise, are observed at a pump rate in which a population inversion is not created yet. A physical interpretation for lasing without inversion in a microcavity is given on the basis of a photon recycling picture consisting of dissipation-free stimulated emission and re-absorption.

 

139.    Y. Yamamoto, S. Machida, and G. Bjork

            "Microcavity Semiconductor-Laser With Enhanced Spontaneous Emission"

            Phys. Rev. A 44 (1), 657-668 (1991).

 

            ABSTRACT: A metal-clad optical waveguide with a semiconductro microcavity structure is proposed to increase the coupling efficiency of spontaneous emission into a lasing mode (spontaneous emission coefficient-beta) and to increase a total spontaneous emission rate simultaneously. Such a microcavity semiconductor laser with enhanced spontaneous emission has novel characteristics, including high quantum efficiency, low threshold pump rate, broad modulation bandwidth, and intensity noise reduced to below the shot-noise limit (amplitude squeezing).

 

140.    Y. Yamamoto, S. Machida, Y. Horikoshi, K. Igeta, and G. Bjork

            "Enhanced And Inhibited Spontaneous Emission Of Free-Excitons In Gaas Quantum-Wells In A Microcavity"

            Opt. Commun. 80 (5-6), 337-342 (1991).

 

            ABSTRACT: Spontaneous emission of the free excitons in GaAs quantum wells in a microcavity is enhanced (X 130) or inhibited (X 1/30) by placing excitonic dipoles at either a resonant wavelength and anti-node position or an off-resonant wavelength and node position of the standing-wave vacuum field fluctuations. The resulting spontaneous radiation pattern is highly concentrated into the normal direction for the enhancement case and the spontaneous emission coupling efficiency into a single microcavity resonant mode is estimated to be 0.3. It is expected that semiconductor lasers with substantially reduced threshold currents can be constructed using such a structure.

 

141.    M. Yamanishi and Y. Yamamoto

            "An Ultimately Low-Threshold Semiconductor-Laser With Separate Quantum Confinements Of Single Field Mode And Single Electron-Hole Pair"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (1A), L60-L63 (1991).

 

            ABSTRACT: A novel semiconductor surface-emitting laser structure is proposed. All spontaneous emission is coupled into a single lasing mode by means of a quantum microcavity, and discrete electron-hole pair emission is made free of absorption by means of a dc-biased quantum dot. The quantum microcavity modified the angle distribution of a vacuum field fluctuation that is a source of spontaneous emission. The dc-biased quantum dot separates the emission and absorption lines by image-charge-induced change in the electric field. The threshold current of such a semiconductor laser can be reduced to below 100 nA.

 

142.    M. Yamanishi, Y. Yamamoto, and T. Shiotani

            "A Novel Modulation Scheme In Semiconductor Light Emitters With Quantum Microcavities - High-Speed Intensity Modulation By Switching Of Coupling Efficiency Of Spontaneous Emission"

            IEEE Photonics Technol. Lett. 3 (10), 888-890 (1991).

 

            ABSTRACT: A modulation of coupling efficiency of spontaneous emission is proposed theoretically to result in an ultrawide band modulation of spontaneous output intensity in semiconductor light emitting devices with quantum microcavities. The proposed modulation scheme does not involve changes in carrier population at all but relies purely on the modulation of the coupling efficiency of spontaneous emission caused by electric field-induced tuning of emission wavelength. An extremely wide-band modulation is predicted showing a cutoff frequency over 10(11) Hz and being completely free of recombination lifetime limitation.

 

143.    A. Yamashita and A. Kawana

            "Nerve Growth Factor-Induced Intracellular Calcium-Ion Release In Chick Dorsal-Root Ganglion Neurons"

            Neurosci. Lett. 128 (2), 147-149 (1991).

 

            ABSTRACT: Nerve growth factor (NGF) rapidly infused into the extracellular medium near cell bodies of cultured chick dorsal root ganglion neurons caused transient increases in intracellular calcium ions, which was detected by fura-2 fluorometry. Similar increases were also observed in a calcium-free medium. There was typically a delay of 20 min between NGF infusion and the release of calcium ions, and this delay was longer when NGF was applied at neurite tips. This is probably because NGF must be transported from neurites to the cell body, where calcium ions are released from intracellular stores.

 

144.    Y. Yamauchi and N. Kobayashi

            "Pyrolysis Of Organo-As Precursors Studied By Surface Photoabsorption"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (12B), L2073-L2076 (1991).

 

            ABSTRACT: Surface Photo-Absorption (SPA) is an in situ optical technique for monitoring growth processes. It can measure the dynamics of surface reaction on a growth surface. We use SPA to investigate the pyrolysis of As precursors such as organo-arsenic and arsine (AsH3), and estimate the decomposition activation energies of these As precursors. The results indicate that tertiary butylarsine (tBAs), diethylarsine (DEAsH) and AsH3 which all contain a hydrogen-As bond, have lower activation energies than might be expected from the average bond strength, indicating that their pyrolysis processes are well catalyzed by the GaAs surface. On ther other hand, trialkylarsine such as trimethylarsine (TMAs) and triethylarsine (TEAs) have high activation energies. As expected from the low activation energy, high-quality GaAs can be grown using tBAs.

 

145.    Y. Yamauchi, N. Kobayashi, and Y. Horikoshi

            "Insitu Optical Observation Of Surface Kinetics During Gaas Metalorganic Chemical Vapor-Deposition"

            Jpn. J. Appl. Phys. Part 2 - Lett. 30 (5B), L918-L920 (1991).

 

            ABSTRACT: GaAs growth process is investigated by in situ optical methods during metalorganic chemical vapor deposition. Formation and annihilation of Ga droplets are observed on GaAs surface, using surface photo-absorption and scattered light observations. When triethylgallium is supplied in excess of one Ga atomic layer coverage to the As-stabilized surface, the scattered light is observed after the saturation of reflectivity due to surface photo-absorption, indicating Ga droplet formation on the surface. AsH3 supply to the surface with Ga droplets results in the annihilation of these droplets followed by the formation of the As-stabilized surface. These are observed, respectively, from the decay of scattered light intensity and subsequent decay of reflectivity of the surface photo-absorption.

 

146.    T. Yanagawa, H. Nakano, and Y. Sasaki

            "Photodarkening And Microcrystallite Size In Colored Filter Glasses"

            Appl. Phys. Lett. 59 (14), 1690-1692 (1991).

 

            ABSTRACT: It is demonstrated for the first time that photodarkening in colored filter glasses is associated with apparent growth of CdSxSe1-x microcrystallites. This is thought to be due to the attraction of impurity ions around the microcrystallites. Both a Q-switched Nd3+:YAG laser and a hybrid mode-locked dye laser are used as the light sources. Microcrystallite growth is directly observed by transmission electron microscopy and by field-emission scanning electron microscopy. Growth is also inferred from local changes in color and measured absorption spectra.

 

147.    T. Yanagawa and L. K. Samanta

            "Increased 2nd Harmonic Output Power Using Walk-Off Compensation In Birefringent Crystals"

            J. Phys.-Condes. Matter 3 (38), 7421-7433 (1991).

 

            ABSTRACT: A new technique utilizing the double refraction walk-off of a precisely cut pair of KTP crystals and a mode-locked Nd:YAG laser to obtain efficient second harmonic generation (SHG) is reported for the first time. This technique leads to a fourfold increment in second harmonic output power compared with that of a single crystal and would open up a number of potential new applications.

 

148.    R. Yano, M. Mitsunaga, and N. Uesugi

            "Ultralong Optical Dephasing Time In Eu3+-Y2sio5"

            Opt. Lett. 16 (23), 1884-1886 (1991).

 

            ABSTRACT: We report what is to our knowledge the first measurement of linear and nonlinear spectroscopic properties for the 7F0-5D0 transition of Eu3+:Y2SiO5. Two clearly resolved lines at 579.879 and 580.049 nm, stemming from different sites, show dissimilar photoluminescence and hole spectra. In addition, these two sites have different inhomogeneous and homogeneous linewidths, which suggests that the local-field effect is smaller for one site. Specifically, the less affected site exhibits the longest dephasing time (822-mu-s) of any solid, which corresponds to a homogeneous linewidth of 387 Hz, and this linewidth is found to persist for hours without apparent spectral diffusion.

 

149.    S. J. Yu, H. Asahi, J. Takizawa, K. Asami, S. Emura, S. Gonda, H. Kubo, C. Hamaguchi, and Y. Hirayama

            "Disordering Of Ingaas/Inp Superlattice And Fabrication Of Quantum Wires By Focused Ga Ion-Beam"

            J. Vac. Sci. Technol. B 9 (5), 2683-2686 (1991).

 

            ABSTRACT: The disordering and compositional change of the InGaAs/InP superlattice by the Ga ion beam was investigated, and using the effect, quantum wires were fabricated by focused Ga ion beam. The analysis of Raman scattering shows that in the implanted region intermixing, i.e., alloying takes place in such a way that the intermixed In1-xGaxAsyP1-y alloy has the compositions of alloy with the lattice constant nearly equal to that of InP, although at higher doses the compositions x and y become smaller due to larger interdiffusion. Focused Ga ion beam of 100 kV was irradiated in lines onto InP (350 angstrom)/InGaAs (50 angstrom) single quantum well at doses of 1 x 10(13) - 1 x 10(14) cm-2. Implanted samples were annealed at 650-670-degrees-C for 60 min. The photoluminescence measurements at 30 K for wires with various widths show that with decreasing wire width the luminescence peak energy increases nearly following the change of the quantum levels in the potential well calculated by taking into account lateral straggling of implanted Ga ions. The implanted and alloyed regions are confirmed to act as potential barriers by which carriers are confined.