Hole-level structure of double δ-doped quantum wells in Si: The influence of the split-off band

We present the electronic structure calculation of two closely p-type δ-doped quantum wells within the lines of the Thomas-Fermi-Dirac (TFD) theory. The distance between the impurity planes as well as the impurity density of the δ-doped wells is varied. The exchange effects are also considered in the present study. We have paid special attention to the split-off band and its influence on the subband hole levels. We also calculate the mobility ratio of double δ-doped (DDD) quantum wells in Si with respect to a single δ-doped (SDD) one, finding the optimum distance between the wells for maximum mobility. Our results are in a good agreement with respect to the experimental data available.