The antisite and interstitial P defects were studied by using pseudopotential total-energy calculations to determine their roles in p-type doping. The results suggested that the difficulty of p-type doping with P was caused by the compensation of shallow acceptors by antisite defects, PZn; which acted as triple donors. A microscopic model was also proposed for 2 ionization levels of P acceptors; one of which was shallow (0.084eV) while the other was deep (0.6 to 0.7eV). The shallow level was attributed to the presence of P at a Se site, while the deep level was attributed to the 2+ charge state of an interstitial P atom near to the hexagonal interstitial site.

K.W.Kwak, D.Vanderbilt, R.D.King-Smith: Physical Review B, 1994, 50[4], 2711-4