Theoretical Investigations of Electronic Processes in Semiconductors: Defects in Zinc Selenide

Wide band-gap semiconductors typically can be doped either n-type or p-type, but not both. Compensation by native defects has often been invoked as the source of this difficulty. We examine the wide band-gap semiconductor ZnSe with first-principles total-energy calculations, using an all-new mixed basis program for an accurate description of the material. We show that native defect concentrations are too low to cause compensation in ZnSe. We further find that, for non-stoichiometric ZnSe, native defects compensate both n-type and p-type material; thus deviations from stoichiometry cannot explain why ZnSe can be doped only one way. In the absence of a generic mechanism, specific dopants should be examined case by case. For Li _{rm Zn}, a promising acceptor, we find that doping may be impeded due to a concentration -dependent reaction.