Chloride MBE of Copper Gallium Disulfide

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A novel epitaxial growth technique of copper gallium disulfide (CuGaS_2) has been developed, that is chloride MBE growth. The c-axis epitaxial films of CuGaS_2 were grown on GaAS(100) substrtates using copper monochloride (CuCl), metallic Gallium (Ga) and sulfur (S) as source materials. The effects of CuCl/Ga supply ratio on the surface morphology and X-ray diffraction intensity of the grown layrs were studied. The Cu/Ga composition in the grown layrs remained to be about unity while the CuCl/Ga supply ratio changed from 0.5to 1.0. High quality epitaxial layrs of CuGaS_2 were grown at 650ﾟC under conditions of slightly excess supply of Ga source. Undoped layrs were highly resistive of 10^4-10^5 OMEGA cm. Photoluminescence (PL) spectra depended on the CuCl/Ga supply ratio. Emission bands at 2.2 and 1.8 eV at 10 K were observed from layrs grown with the CuCl/Ga supply ratio of 0.87-1.05 and 0.49-0.65, respectively.Low resistive p-type conduction as low as 10 OMEGA cm were attained by Zn doping. The resistivety became lower with increasing the CuCl/Ga supply ratio, which suggested that Zn atoms were introduced into the Ga sites of CuGaS_2 lattice and formed acceptor levels. New PL bands at 2.3 and 2.4 eV were observed from the Zn doped layrs, and the PL bands had properties of donor-acceptor pair emissions. P-type layrs with resistivities lower than 0.1 OMEGA cm were obtained by Sn doping.