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 × 1017 cm−3. The best Hall electron mobility for this composition was 1570 cm2 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.