Improved model-solid-theory calculations for valence-band offsets at semiconductor-semiconductor interfaces

The model-solid theory (MST) of Van de Walle and Martin is widely used for estimating valence-band offsets (VBO’s) at semiconductor-semiconductor interfaces. We present reliable MST parameters calculated using a self-consistent pseudopotential technique. In both our calculations and those of Van de Walle and Martin, the semicore d electrons are treated as core electrons, but in our calculations their overlap with the valence electrons is accounted for by using nonlinear core exchange-correlation corrections. The accuracy of these parameters is checked by calculating the VBO’s at eighteen lattice-matched interfaces; the results are in quantitative agreement with experimental data and with all-electron calculations which treat the above d electrons as valence states, including ${\mathit{A}}^{\mathrm{II}}$ ${\mathit{B}}^{\mathrm{VI}}$/${\mathit{C}}^{\mathrm{IV}}$ and ${\mathit{A}}^{\mathrm{II}}$ ${\mathit{B}}^{\mathrm{VI}}$/${\mathit{C}}^{\mathrm{III}}$ ${\mathit{D}}^{\mathrm{V}}$ interfaces. Moreover, VBO’s at strained ZnSe/ZnS interfaces are calculated and found to be in good agreement with the available experimental data. Although the VBO’s are reproduced very well by our calculations, the fundamental band gaps at the Γ point are found to be significantly larger than those calculated using all-electron techniques.