Deposition and characterization of gallium arsenide films for solar cells applications

Gallium arsenide films have been deposited on tungsten-coated graphite substrates by the reaction of gallium, hydrogen chloride, and arsine in a hydrogen flow. It has been found that the presence of hydrogen chloride in the gallium monochloride-arsenic mixture is essential in obtaining large-area gallium arsenide films with sufficiently good microstructure suitable for photovoltaic devices. Schottky-barrier and MOS structures have been prepared from n-GaAs/n⁺-GaAs films on tungsten/graphite substrates, and their electrical properties investigated. Under AM1 conditions, MOS structures of 9-cm²area have conversion efficiencies of up to 4.4 percent (without antireflection (AR) coating, would be about 6.7 percent with proper coating), and the conversion efficiencies can be increased to 5 percent (without AR coating, would be about 7.5 percent with proper coating) by using a thin gallium arsenide-phosphide film at the surface of gallium arsenide.