Surface vacancies in II-VI and 111-V zinc blende semiconductors•>

We present calculations of the bound state energy levels of ideal vacancies near the ( 110) surface of some zinc blende II-VI and Ill-Y semiconductors: CdTe, ZnTe, GaAs, AlAs, InAs, and some alloys among them. Here we compare vacancies near the surface ofii-VI's with those ofiii-V's. In contrast to the III-V's, where a neutral vacancy has an odd number of electrons, a neutral vacancy in a II-VI semiconductor has an even number. We find that single anion vacancies in Ill-Y's can behave as both donors and acceptors, and follow observed trends with ionicity and alloy composition. We also find that single cation vacancies in II-VI's behave as double acceptors and the anion vacancies behave as shallow double donors. We suggest experiments to test the importance of vacancies in determining the Fermi level pinning position for II-VI's.