Homo-epitaxial growth of ZnSe by vapor phase epitaxy and characterization of the grown layers

Abstract

From photoluminescence measurements, the main contamination of vapor-phase homo-epitaxial ZnSe layers grown on substrates prepared by the Bridgman method was found to be due to Ga, Li, and Na, originating from the substrates. The contamination due to Li and Ga and the surface morphology of the homo-epitaxial layers were shown to be controllable to a certain extent by the vapor pressure ratio of Zn to Se, and the observed reduction of resistivities in homo-epitaxial layers compared to the substrates was interpreted in terms of a decrease of acceptor impurities. From the measured photoluminescence intensity ratio of donor-bound-excitons to free-excitons, the donor concentration of a homo-epitaxial layer grown at 540°C was estimated to be about 0.5−2.0 × 10 15 cm −3, being 2–4 times lower than that of the substrate. The comparison of measured etch pit densities between a homo-epitaxial layer and the substrate indicates that the reduction of defect densities of ZnSe substrates is essential to obtain high-quality homo-epitaxial layers with low defect densities.