InAs Nanowire-channel Field Effect Transistors

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Guoqiang Zhang, Kouta Tateno, and Hidetoshi Nakano
Optical Science Laboratory

@@Recently, nanowires (NWs) have become the center of attention due to the exceptional versatility and promise a wide range of potential applications, from electronics and photonics to biochemistry and medicine [1]. Semiconductor NWs are expected to play an important role as functional device elements in nanoscale electronic devices. InAs NWs are very promising for high-speed device applications due to their high mobility. We have established a reproducible fabrication process for NW field effect transistors (FETs) and the performance of the InAs NW-channel FETs were evaluated [2].
@@Au colloidal particles were used as the catalyst for the growth of InAs NWs by vapor-liquid-solid mode in a low-pressure (76 Torr) metalorganic vapor phase epitaxy system [3]. The precursors were trimethyl-indium and AsH3. Transmission electron microscopy measurement indicates that the NWs are wurtzite-structure without stacking faults. The NWs were dispersed on a SiO2/Si (SiO2 thickness: 500 nm) substrate and then Ni/Au metals were selectively deposited on the NWs to form electrical contacts after patterning by electron beam lithography. The contacts were annealed at 300 Ž for 30 s by rapid thermal processing. Figure 1 shows a NW-channel FET with a number of electrodes.
@@Using the underlying heavily doped Si substrate as the gate electrode, we measured the DC characteristics of InAs NW-channel FETs with a semiconductor parameter analyzer at room temperature. Figure 2 shows typical characteristics of Id-Vd of 2 and 4-terminal measurements. Compared with NW resistance, the contact resistance is very small and the specific contact resistivity is estimated to be 2.0~10-7 ƒ¶cm2. Figure 3 shows typical Id-Vg characteristics at different drain voltages. The feature that the current increases with the gate voltage indicates that the NW is n-type. The NW-channel FETs show a maximum transconductance (gm) in the range of 0.24-0.36 µS at Vd of 0.1 V. For FET devices, the normalized transconductance g*m = gm/wg is an important figure of merit, where wg is the channel width (in the case of NW channel, the width is the NW diameter). The g*m varies in the range of 2.5-3.7 mS/mm at Vd of 0.1 V. Based on the FET properties, the electron concentration (N) and mobility (µ) of the NW segment could be estimated. N and µ are in the range of 2.3-5.8~1017 cm-3 and 1.29-1.53~103 cm2V-1 s-1, respectively. We are investigating how to further improve the FET properties and fabricate functional quantum devices.
@@This work was partly supported by JSPS-KAKENHI (16206003, 18310074).

[1] Y. Li, et al., Mater. Today 9(10) (2006) 18; C. Thelander, et al., ibid. 9(10) (2006) 28; P. J. Pauzauskie and P. Yang, ibid. 9(10) (2006) 36.
[2] G. Zhang, et al., ISCS2007, Kyoto, Japan, Oct. 2007, p. 142.
[3] G. Zhang, et al., J. Appl. Phys. 103 (2008) 014301.

Fig. 1. SEM image of a InAs NWFET.
Fig. 2. Vd-Id characteristics of 2 and 4-terminal measurements.
Fig. 3. Id-Vg characteristics at various drain voltages.

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