Density functional and tight binding theories of electronic properties of II-VI heterostructures

We present comparative calculations of the electronic structure of Cd and Zn based group II-VI compounds and their heterostructures based on the density functional and tight binding theories. The first principles density functional theory (DFT) uses the modified Becke-Johnson exchange potential with LDA correlation potential (MBJLDA) and the semi-empirical tight binding theory uses the first nearest neighbor (NN) sp3d5 and second nearest neighbor (2NN) sp3s⁎ basis with spin-orbit coupling of II cation (Cd, Zn) and VI anion (S, Se, Te) atoms for calculating the electronic structure of Cd and Zn based II-VI compounds and their heterostructures. The results of DFT with MBJLDA functional and NN sp3d5 and 2NN sp3s⁎ TB models are found to be in excellent agreement with measured band gaps of CdX and ZnX (X=S, Se, Te) based group II-VI compounds and their CdZnS/CdS, CdSTe/CdTe and ZnSSe/ZnSe heterostructures. We conclude that the NN sp3d5 TB model gives much more physical insight than the (2NN) sp3s⁎ TB model, making use of the fictitious s* state unnecessary.