Nonparabolicity corrections to the valence band energy levels of Si/GexSi1-x quantum wells

In earlier work, subband energies of Si/Ge_xSi_1-x quantum wells were obtained neglecting valence band nonparabolicity. Here we present an algorithm for solving for the energies and wavefunctions of the mixed light-hole and split-off subbands under stress, which incorporates the energy dependence of the effective mass exactly. We show that this gives corrections to the energies that are of the order of tens of meV, and results in small nonorthogonality corrections to the envelope wavefunctions. These corrections are discussed for several cases of physical interest and are compared to the results obtained assuming a constant bandedge effective mass.