Semi-empirical tight binding modelling of CdSTe/CdTe, ZnSSe/ZnSe and ZnSSe/ CdSe heterostructures

We present a semi-empirical sp3s⁎ tight binding model to calculate the effects of alloy composition and strain on electronic band structure of Cd and Zn based group II–VI heterostructures for photovoltaic devices. The semi-empirical sp3s⁎ TB model Hamiltonian includes second nearest neighbor interactions and spin-orbit splitting of p-states. Bond lengths and atomic energies of cation and anion forming ternary semiconductors are taken as nonlinear function of composition. The 2NN sp3s⁎ tight binding model calculations are compared with those of the package program WIEN2k which uses the generalized gradient approximation (GGA) and local spin density approximation (LSDA) based scaling law for the scissor operator for the self energy corrections to the DFT energy band gaps of semiconductors. We found that both the GGA and LSDA corrected WIEN 2k simulations and 2NN sp3s⁎ TB model accurately reproduces the band gaps and both the valence band and conduction band dispersion curves at Γ, X and L high symmetry points of Brillouin zone, also in good agreement with experiment.