Efficient electron and hole doping in compositionally abrupt Si/Ge nanowires

Efficient doping in semiconductor nanowires can be a challenging task in materials science. In this study, we explore effects of various dopant elements (P, N, Al, B, and O) on the electronic properties of three types of compositionally abrupt SiGe nanowires (NWs), namely, the core-shell Ge-core/Si-shell and Si-core/Ge-shell NWs, and the fused triangular-prism SiGe NW. Based on the density-functional theory calculations, we find that the substitution of Ge by the pentavalent P at the interfacial region between the core and shell of Ge/Si NWs leads to an easy injection of high-density free-electron-like carriers, whereas the substitution of Si by trivalent Al or B at the interfacial region leads to an easy injection of high-density free-hole-like carriers. However, the introduction of the pentavalent N has little effect on the conductivity of the three types of SiGe NWs. For the divalent O dopant, only the substitution of Si by O in the fused triangular-prism SiGe NW can result in high-density free-hole-like carriers at low temperature. This comprehensive study demonstrates, for the first time, that the doping efficiency not only depends on the type of dopant element (which is well-known) but also on the interfacial geometry of the Si/Ge domains within the compositionally abrupt NWs. The study can offer guidance to the synthesis of novel compositionally abrupt SiGe NWs through a tailored interfacial geometry and controlled interfacial doping.