Theory of the channel-width dependence of the low-temperature hole mobility in Ge-rich narrow square Si/SiGe/Si quantum wells

A theory is given of the mobility of a two-dimensional hole gas (2DHG) at low temperature in narrow square Si/Si1-xGex/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 K mobility of holes in a Si/Si0.2Ge0.8/Si quantum well on the channel width varying from 25-70 angstrom. Further, this provides evidence in favor of screening of short-range interactions such as alloy disorder.