Hole mobility in Ge/Si core/shell nanowires: What could be the optimum?

摘要

Recent experimental works have shown that Ge/Si core/shell nanowires (NWs) are very attractive for nanoelectronics and for low-temperature quantum devices, thanks to the confinement of holes in the Ge core. Reported hole mobilities of the order of 200 cm~2/V/s are promising for high-performance field-effect transistors. However, we demonstrate that mobilities more than ten times higher, up to 8000 cm~2/V/s, could be reached in Ge/Si NWs. Atomistic calculations reveal the considerable influence of the strains induced by the Si shell on the hole transport, whatever the NW orientation. The enhancement of electron-phonon interactions by confinement, which usually degrades the mobility in NWs, is therefore outbalanced by the effect of strains.