Optimized tight‐binding valence bands and heterojunction offsets in strained III‐V semiconductors

An optimized nearest‐neighbor tight‐binding description of valence bands in strained‐layer III‐V semiconductors is developed and applied to the calculation of valence‐band offsets at strained heterojunctions. It is first shown that a single set of universal interatomic matrix elements can be found which, when appropriately scaled for bond length, simultaneously provide near‐optimum tight‐binding predictions of valence‐band uniaxial deformation potentials, trends in photoelectric thresholds, and valence bandwidths for the common III‐V compounds. Application of the optimized tight‐binding model to the calculation of valence‐band offsets at strained heterojunctions is then discussed, and one simple approach is described which combines a fully strain‐dependent version of the optimized tight‐binding model with Tersoff’s quantum‐dipole heterojunction model. Offsets calculated using this combined approach are shown to agree with experimental data better than either strain‐dependent natural tight‐binding offsets or offsets calculated directly from Tersoff’s model. Finally, convenient quadratic expressions for the composition dependence of light‐and heavy‐hole valence‐band offsets, as calculated using the combined approach, are tabulated for several strained and unstrained ternary‐on‐binary III‐V heterojunctions. The balance between accuracy and simplicity offered by our approach should render it useful for exploratory heterojunction device modeling.