Energy levels of isoelectronic impurities by large scale LDA calculations

Abstract

Isoelectronic impurity states are localized states induced by stoichiometric single atom substitutions in bulk semiconductors. Photoluminescence spectra indicate deep impurity levels of 0.5--0.9 eV above the top of the valence band for such systems as GaN:As, GaN:P, CdS:Te, and ZnS:Te. Previous calculations based on small supercells seemingly confirmed these experimental results. However, the current ab initio calculations based on thousand-atom supercells indicate that the impurity levels of the above systems are actually much shallower (0.05--0.20 eV), and these impurity levels should be compared with photoluminescence excitation spectra, not photoluminescence spectra.