VAPOR-PHASE EPITAXY OF CUGAS2 USING METAL CHLORIDES AND H2S SOURCES

VPE growth of CuGaS2 on GaAs and ZnS/GaAs substrates has been performed using metal chlorides and H2S+Ar or H2S+H2 gas as a sulfur source. X-ray diffraction studies showed that the epitaxial growth of singly oriented crystals with their chalcopyrite c-axis normal to the (100) GaAs surface can occur in spite of the large difference in the layer and substrate lattice constants. With (100) ZnS/GaAs substrates, the dominant growth occurred with the c-axis parallel to the substrate surface. X-ray, Raman and EPMA studies indicated the necessity of further efforts to improve the layer uniformity. The low temperature photoluminescence spectrum of the grown layer was found to be surprisingly similar for position-to-position changes in the sample, and also for sample-to-sample changes. The photoluminescence of the layer on GaAs substrates exhibited a main emission peak at 2.31 eV, and three bound exciton lines in addition to a line due to free excitons. Analysis of the time-resolved spectra of the 2.31 eV emission gave the relevant donor and acceptor binding energies to be 185 ± 10 meV and 120 ± 10 meV, respectively. A brief discussion is given on the origin of this acceptor in terms of observed low-resistivity of the grown layer. © 1990, Elsevier Science Publishers B.V. (North-Holland). All rights reserved.