Native defects in GaP were studied using a pseudopotential density functional theory method in order to determine their relative concentrations and the most stable charge states. The electronic and atomic structures were presented and the defect concentrations were estimated using calculated formation energies. Relaxation effects were taken into account fully and produce negative-U charge transfer levels for VP and PGa. The concentration of VGa was in good agreement with the results of positron annihilation experiments. The charge transfer levels presented compare qualitatively well with experiments where available. The effect of stoichiometry on the defect concentrations was also described and was shown to be considerable. The lowest formation energies were found for PGa2+ in p-type and VGa3- in n-type GaP under P-rich conditions, and for GaP2- in n-type GaP under Ga-rich conditions. Finally, the finite size errors arising from the use of super-cells with periodic boundary conditions were examined.

Relative Concentration and Structure of Native Defects in GaP. A.Höglund, C.W.M.Castleton, S.Mirbt: Physical Review B, 2005, 72[19], 195213 (16pp)