Interface roughness effect on density of states and mobility of narrow Si/Si1-xGex quantum wells: path-integral approach

The in-plane transport of a two-dimensional hole gas in narrow Si/Si1-xGex quantum wells (QWs) with the interface roughness effect was investigated using path-integral theory. The random variation of the well width causes the fluctuation potential in the in-plane direction. This fluctuation was integrated into the path integral via the eigenvalue model of the infinite barrier height QW. The hole mobility and the density of states can be derived in an analytic form. The calculated hole mobility was compared with the experimental data and a different theoretical approach based on the wavefunction model. We found that Δ = 0.2 nm and Λ = 4.5 nm give a good description of the experimental data. Our theory predicted the existence of the localized states, which reduces the hole mobility in addition to the prediction from the wavefunction method.