The role of interface in unpassivated Si3-xGex heterostructure nanowires along the <111> direction

First-principles calculations have been applied to investigate electronic and piezoresistive properties of Si3-xGex heterostructure nanowires along <;111> direction. It is shown that Si3-xGex heterostructure nanowires with clear interfaces present semiconductor-like band lineups, while those with mixed interfaces present metal-like band lineups. The piezoresistive effects in Si3-xGex heterostructure nanowires with clear interfaces are much more notable than those with mixed interfaces, and they are also larger than the piezoresistive effects in prestine Si nanowires. The piezoresistance coefficient of Si2Ge1 heterostructure nanowires is up to -132×10^-11 Pa^-1, which is about 2.5 times of pristine Si nanowires. On the contrary, Si1.5Ge1.5 is almost free of external axial strain. It can be predicted that Si3-xGex heterostructure nanowires with clear interfaces have potential application in future nanowire-based sensors.