16:15 〜 16:30
▲ [19p-221A-12] Hole gas accumulation in core-shell nanowires formed by Si and Ge
キーワード：Si/Ge nanowires, VLS
Core-shell nanowires (NWs) synthesized by silicon (Si) and germanium (Ge) have been suggested as building blocks of vertical-type metal-oxide-semiconductor field-effect transistors (MOSFETs) with high speed and low energy consumption [1-3]. Impurity doping in the core and shell regions is essential to give a function in MOSFETs whereas impurity scattering need to be considered [2,3]. To suppress the impurity scattering, high electron mobility transistor (HEMT) structures has to be formed in core-shell NWs. In this study, impurity doping and lattice stress in the core-shell nanowire structures were studied. The relationship between the core and shell with various diameters and thicknesses was investigated. The p-Si/i-Ge core-shell NWs were synthesized by chemical vapor deposition (CVD) method based on the vapor-liquid-solid (VLS) growth mechanism as shown in Fig. 1. From transmission electron microscopy (TEM) with EDX measurements, the core-shell NW structure showed good crystallinity and sharp interface as shown in Fig. 2. Lattice stress and doping effect in the core-shell structures were characterized by X-ray diffraction (XRD) measurements. The Si core region has tensile stress from the Ge layer, while the Ge shell layer has compressive stress from the Si core NW. Hole gas accumulation in the i-Ge shell region was detected by forming the sharp interface between Si and Ge and precisely controlling selective doping in the p-Si core NW. This result indicates that carrier transport region can be separated from the impurity doped region and therefore suppressed impurity scattering. The p-Si/i-Ge/p-Si core-double shell NWs were also fabricated to more clearly demonstrate the hole gas accumulation and its enhancement in the i-Ge layer. These results show that impurity scattering can be effectively suppressed by constructing core-shell structures.