First-principles study of antisite and interstitial phosphorus impurities in ZnSe

The antisite and interstitial phosphorus defects in ZnSe have been studied by pseudopotential total-energy calculations to investigate their roles in the p-type doping problem of ZnSe. Our calculations suggest that the difficulty in p-type doping of ZnSe with phosphorus is caused by the compensation of shallow acceptors by the antisite defects PZn, which act as triple donors. A microscopic model for two ionization levels of phosphorus acceptors in ZnSe (one shallow at 84±4 meV and one deep at 0.6-0.7 eV) is also proposed. The shallow acceptor level is attributed to a P substituted at a Se site, while the deep acceptor is assigned to the 2+ charge state of an interstitial P atom near the hexagonal interstitial site.