It is well known that there is an increasing demand for high- performance electronic devices in nowadays world, traditional types of metal-oxide-semiconductor field-effect transistors (MOSFETs) can no longer satisfy the performance requirements. The focus has shifted to pushing the limits of their structural physics scales and materials. In order to address impurity scattering, and short-channel effects (SCE) associated with device miniaturization, new structures have been developed. Gate-all-around (GAA) FETs supports significantly reducing SCE and being able to separate the doping region from the conducting region while enhancing drive current. Undoped Ge and Boron-doped Si are decided as core and shell. The reasons are the high mobility of Ge and energy band-offsets in the heterojunction. Depending on the Fermi level position, hole gas can be accumulated in the quantum well.
In this study, we focused on top-down method to fabricate vertical type Ge/Si core/shell NWs, demonstrate hole gas accumulation in the NW as evidence of successful fabrication and compare the level of Fano effect produced between different size NWs.