Theory of the channel-width dependence of the low-temperature hole mobility in Ge-rich narrow squareSi∕SiGe∕Siquantum wells

Abstract

A theory is given of the mobility of a two-dimensional hole gas (2DHG) at low temperature in narrow square $\mathrm{Si}∕{\mathrm{Si}}_{1\ensuremath{-}x}{\mathrm{Ge}}_{x}∕\mathrm{Si}$ quantum wells at high Ge content. Different from the previous treatment, we have carried out a proper calculation of the misfit deformation potential and 2DHG screening. As a result, the scattering mechanisms due to surface roughness, misfit deformation potential, and alloy disorder are found to dominate the 2DHG mobility. Our theory enables a very good quantitative description of recently measured data about the dependence of the $8\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ mobility of holes in a $\mathrm{Si}∕{\mathrm{Si}}_{0.2}{\mathrm{Ge}}_{0.8}∕\mathrm{Si}$ quantum well on the channel width varying from $25--70\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$. Further, this provides evidence in favor of screening of short-range interactions such as alloy disorder.