A theoretical study of native acceptors in CdGeAs2

Native acceptor centres in CdGeAs2 are studied using atomistic simulation techniques for which a new set of interatomic potential parameters consisting of two- and three-body terms is developed. Crystal lattice constants, elastic and low- and high-frequency dielectric constants are well reproduced in this atomistic model. The calculated formation energies for vacancies, interstitials and antisites in this material suggest that the intrinsic disorder is dominated by antisites in the cation sublattice followed by the Schottky and Frenkel defects. The acceptor centre identified by Hall-effect measurements and EPR is found to be related to the delocalized hole shared by the four As neighbours bound to CdGe. For this centre, calculations yield a binding energy of 0.13 eV in an agreement with the experimental value of 0.15 eV obtained by the Hall-effect measurements. Furthermore calculations provide the magnitude of the lattice distortion introduced by this acceptor centre in CdGeAs2 which can be used for the analysis of ENDOR experiments.