DOPING LIMITS IN ZNSE

We explore doping problems in p-type ZnSe using ab initio total-energy calculations. Our method determines the formation energies of native point defects and of acceptor dopants as a function of the relative abundance of Zn, Se and the dopant atoms, resulting in a map of the concentrations of defects and dopants over the entire thermodynamically allowed range of conditions. For native point defects, which were often assumed to compensate the doping of ZnSe, we show that their concentrations are negligibly small over most of the range of allowed stoichiometry. For a ZnSe acceptor-doped with Li(Zn) or Na(Zn), we find that compensation by Li(i) and Na(i) donors is possible, but can be avoided in a sufficiently Se-rich environment. The most stringent limits on acceptor doping of ZnSe come from the solubility limits of the three dopants. Our calculations show that Na(Zn) has a very low solubility limit, with a much higher limit for Li(Zn), and the highest for N(Se).