First-principles study of phosphorus and nitrogen impurities in ZnSe.

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Phosphorus and nitrogen defects in ZnSe have been studied by pseudopotential total-energy calculations. Various charge states of the phosphorus and nitrogen impurities ocupying zinc sites (antisite defects) and interstitial sites (interstitial defects) were considered: their structural and electronic properties were investigated, and formation energies were calculated as a function of Se and electronic chemical potentials. The calculated electronic properties and formation energies were used in the investigation of the role of impurities in the p-type doping problem of ZnSe. Our study suggests that the difficulty with p-type doping of ZnSe by phosphorus results from the compensation of the shallow acceptors by the antisite defects ${\mathrm{P}}_{\mathrm{Zn}}$ which act as triple donors. In the case of nitrogen, the concentrations of the antisite and interstitial defects are too low to cause such compensation, which is consistent with the successful p-type doping of ZnSe with nitrogen.