Gate Operation of InAs/AlGaSb Heterostructures with an Atomic-Layer-Deposited Insulating Layer
Kyoichi Suzuki, Yuichi Harada, Fumihiko Maeda*,
Koji Onomitsu, Toru Yamaguchi, and Koji Muraki
Physical Science Laboratory, *Materials Science Laboratory
InAs/AlGaSb heterostructures are promising for applications to high-speed electronic devices, such as high-frequency field-effect transistors, because of their large electron concentration and high room-temperature electron mobility. There remains a serious impediment to achieving the expected device characteristics, however, posed by the large gate leakage through the AlGaSb barrier and GaSb cap layers. To circumvent this difficulty, various methods of fabricating a gate insulator have been examined. In particular, atomic layer deposition (ALD), which makes it possible to deposit a thin and uniform insulating layer with high dielectric constant, is considered to be an up-and-coming technique [1,2].
It is well known in the InAs/AlGaSb system that, without any surface treatment, native oxides of the GaSb cap layer and/or defects at the cap/insulator interface induce electron trap states. Accumulation and release of electrons in and out of these trap states partially compensate the gate electric field and thus impede the gate operation. We have investigated the effects of the surface treatments before forming an Al2O3 insulating layer by ALD (Fig. 1) . We find that dilute HCl treatment for only 10 s effectively removes the electron trap states and greatly improves the gate operation (Fig. 2).
 J. E. Crowell, J. Vac. Sci. Technol. A 21 (2003) S88.
 I. J. Gelfand, S. Amasha, D. M. Zumbuhl, M. A. Kastner, C. Kadow, and A. C. Gossard, Appl. Phys. Lett. 88 (2006) 252105.
 K. Suzuki, Y. Harada, F. Maeda, K. Onomitsu, T. Yamaguchi, and K. Muraki, Appl. Phys. Express 4 (2011) 125702.
Fig. 1. InAs/AlGaSb heterostructure with an
Al2O3 insulating layer by ALD.
Fig. 2. Electron concentration (n2d) as a function of gate
voltage (VG). (a)No-treatment. (b)HCl-treatment
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