Modeling of defects in wide-gap semiconductors using cluster approach

Recent work on modeling of spatial configuration of native and impurity defects in wide-band gap semiconductors such as ZnSe and GaN was reviewed. The calculations were performed by semi-empirical and non-empirical SCF MO LCAO method in the frame of the cluster approach, with full energetic optimization of the spatial atomic configurations. In ZnSe, the calculations allowed to rule out some spatial configurations of nitrogen-related defects discussed in the literature. A metastable behavior of nitrogen-related defects was predicted, and the correlation of the results of modeling with transformation of excitonic photoluminescence spectra after annealing was observed. For wurtzite type GaN, incorporation of Si in GaN lattice sites on Ga place leads to the lattice relaxation including an increase of the c lattice parameter with simultaneous decrease of the a parameter. The result is the reduction of compressive strain in GaN grown on sapphire, in accordance with the data of reflection spectra, or the increase of tensile strain in GaN/Si, in accordance with the literature data. In GaN, calculated spatial configurations showed both anisotropic and isotropic type of lattice relaxation, depending on the nature of impurity. The importance of defect modeling in heteroepitaxial heterostructures taking into account lattice mismatch strain is discussed.