Scattering mechanisms in Si/SiGe quantum wells

Motivated by recent experiments of Si/SiGe quantum wells with a codesign of high mobility and large valley splitting [B. Paquelet Wuetz, et al., Nature Communications 14, 1385 (2023); D. D. Esposti, et al., arXiv:2309.02832], we examine contributions to mobility and quantum mobility from various scattering mechanisms and their dependencies on the electron density. We find that at low electron densities, n_e<4.0×10 cm^-2, the transport mobility is limited by charged impurities outside the quantum well. Consideration of other scattering mechanisms indicates that interface roughness is a likely limiting factor of transport mobility at higher densities. We estimate the critical density of metal-insulator transition using the Anderson-Ioffe-Regel condition. For quantum mobility, our calculation suggests background and remote impurities are likely the limiting scattering sources at all densities. Future measurements of quantum mobility should yield more information on the distribution of background impurities inside the SiGe barriers and remote impurities at the semiconductor-oxide interface.