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

We report the heteroepitaxial growth of variable composition n-GaAs1-xPx directly on GaAs substrates via close-spaced vapor transport using mixed GaAs-GaP powder sources. GaAs1-xPx films showed an average 10% reduction in atomic concentration of phosphorous from the source material, and ten GaAs0.7P0.3 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-GaAs0.7P0.3 with a carrier concentration of 2 x 10(17) cm(-3). The best Hall electron mobility for this composition was 1570 cm(2) V-1 s(-1). Cross-sectional transmission electron microscopy of GaAs0.7P0.3 shows single-crystal structure with few defects. We conclude that CSVT is a promising route to the growth of ternary III-V materials like GaAs1-xPx for low-cost high-efficiency tandem photoelectrochemical or photovoltaic devices.