The diffusion mechanism of Zn in GaP and InP was investigated using first-principles computational methods. It was found that the kick-out mechanism was the favored diffusion process under all doping conditions for InP, and under all except n-type conditions for GaP. In n-type GaP, the dissociative mechanism was probable. In both p-type GaP and InP, the diffusing species was found to be Zni2+. The activation energy for the kick-out process was 2.49eV in GaP and 1.60eV in InP, and therefore unintentional diffusion of Zn was expected be a greater concern in InP than in GaP. The dependence of the activation energy upon both the doping conditions of the material and upon the stoichiometry was explained, and found to be in qualitative agreement with the experimentally observed dependences. The calculated activation energies agreed reasonably well with experimental data, assuming that the region from which Zn diffused was p-type. Explanations were also found as to why Zn tended to accumulate at pn junctions in InP and to why a relatively low fraction of Zn was found on substitutional sites in InP.

Diffusion Mechanism of Zn in InP and GaP from First Principles. A.Höglund, C.W.M.Castleton, S.Mirbt: Physical Review B, 2008, 77[11], 113201 (4pp)