Key scattering mechanisms for holes in strained SiGe/Ge/SiGe square quantum wells

Abstract

We present a theory of the low-temperature transport of holes confined in the Ge strained channel of single-side modulation-doped SiGe/Ge/SiGe square quantum wells (QWs). Besides the well-known scattering mechanisms such as remote impurities and surface roughness, the theory includes misfit deformation potential. We prove that due to the effect from doping-induced band bending, the surface roughness and misfit deformation potential scatterings are considerably strengthened. Accordingly, these are found to be the key scattering mechanisms in the SiGe/Ge/SiGe system, which are still a subject under debate. Our theory can explain all recent experimental data about the transport properties of interest, namely, the carrier-density dependences of the hole mobility and the ratio of the transport to quantum lifetimes. Further, the calculated hole mobility in Ge strained QWs exhibits a special channel-width dependence with a sharp peak, which was observed but has not been explained so far. © 2008 American Institute of Physics.