Controlling Catalyst-Free Formation and Hole Gas Accumulation by Fabricating Si/Ge Core-Shell and Si/Ge/Si Core-Double Shell Nanowires.

Abstract

The catalyst-free formation of silicon (Si) and germanium (Ge) core-shell and core-double shell nanowires (NWs) was studied for use as building blocks of high electron (hole) mobility transistors (HEMTs). Vertically aligned <i>p</i>-type Si (<i>p</i>-Si)/intrinsic Ge (<i>i</i>-Ge) core-shell NWs and <i>p</i>-Si/<i>i</i>-Ge/<i>p</i>-Si core-double shell NWs with uniform diameters were formed by combining nanoimprint lithography, Bosch etching, and chemical vapor deposition. The boron (B) doping process was used to prepare <i>p</i>-Si NWs. The hole gas accumulation could be reliably detected from the <i>i</i>-Ge shell region in the <i>p</i>-Si/<i>i</i>-Ge core-shell NW and <i>p</i>-Si/<i>i</i>-Ge/<i>p</i>-Si core-double shell NW arrays through the Fano resonance effect, showing that core-shell NW heterostructures can suppress impurity scattering and act as high-mobility transistor channels. This provides the possibility for the future creation of vertical high-speed transistors.