Gallium arsenide phosphide grown by close-spaced vapor transport from mixed powder sources for low-cost III–V photovoltaic and photoelectrochemical devices

Abstract

We report the heteroepitaxial growth of variable composition n-GaAs_1−xP_x directly on GaAs substrates via close-spaced vapor transport using mixed GaAs–GaP powder sources. GaAs_1−xP_x films showed an average 10% reduction in atomic concentration of phosphorous from the source material, and ten GaAs_0.7P_0.3 films were grown with reproducible composition from a single source pellet. Non-aqueous photoelectrochemical measurements were used to assess electronic quality, with the best short-circuit photocurrent of 6.7 mA cm⁻² and open-circuit photovoltage of 0.915 V for n-GaAs_0.7P_0.3 with a carrier concentration of 2 × 10¹⁷ cm⁻³. The best Hall electron mobility for this composition was 1570 cm² V⁻¹ s⁻¹. Cross-sectional transmission electron microscopy of GaAs_0.7P_0.3 shows single-crystal structure with few defects. We conclude that CSVT is a promising route to the growth of ternary III–V materials like GaAs_1−xP_x for low-cost high-efficiency tandem photoelectrochemical or photovoltaic devices.