Native defects and self-compensation in ZnSe

Wide-band-gap semiconductors typically can be doped either n type or p type, but not both. Compensation by native point 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 a mixed-basis program for an accurate description of the material. Formation energies are calculated for all native point defects in all relevant charge states; the effects of relaxation energies and vibrational entropies are investigated. The results conclusively show that native-point-defect concentrations are too low to cause compensation in stoichiometric ZnSe. We further find that, for nonstoichiometric ZnSe, native point defects compensate both n-type and p-type material; thus deviations from stoichiometry cannot explain why ZnSe can be doped only one way.