ACCEPTOR AND DONOR STATES OF IMPURITIES IN WIDE-BAND GAP II-VI SEMICONDUCTORS

The stability of substitutional versus displaced atomic configurations for N, Al, Ga, Cl, and isoelectronic O impurities in ZnSe, ZnTe, MgSe, and MgTe wide band gap semiconductors were examined via first-principles pseudopotential calculations. Negatively charged DX centers with very large lattice relaxations are found to be the stable states of Al and Ga donor impurities in ZnTe and MgTe but to be high energy metastable states in ZnSe and MgSe. The acceptor state of 0 in ZnSe is identified with a strongly bonded configuration in which a Zn-0 bond replaces a Zn-Se bond. The idea of a beneficial defect-mediated doping mechanism is proposed and applied to an explanation of the properties of N impurities in ZnSe.