DEFECTS IN METALORGANIC CHEMICAL VAPOR-DEPOSITION EPITAXY-GROWN ZNSE FILMS ON GAAS INVESTIGATED BY MONOENERGETIC POSITRONS

Defects in metalorganic chemical vapor deposition epitaxy (MOVPE)-grown ZnSe heteroepilayers on GaAs were investigated by monoenergetic positrons. The present work revealed clear differences between an as-grown specimen and a heat-treated one under different atmospheres. The as-grown specimen prepared at high temperature (350-degrees-C) showed a proliferation of a large number of defects near the surface and at the GaAs interface due to lattice mismatching and nonstoichiometry. Heat treatment at 70-degrees-C in N2 ambient introduced vacancies in high concentrations which contribute to the deep emission of photoluminescence. It is concluded that adequate heat treatment under zinc vapor is essential to reduce the concentration of native defects in MOVPE-grown ZnSe film on GaAs.