Efficient n-GaAs Photoelectrodes Grown by Close-Spaced Vapor Transport from a Solid Source

摘要

n-GaAs films were grown epitaxially on n~+-GaAs substrates by a close-spaced vapor transport method and their photoelectrochemical energy conversion properties studied. Under 100 mW cm~(-2) of ELH solar simulation, conversion efficiencies up to 9.3% for CSVT n-GaAs photoanodes were measured in an unoptimized ferrocene/ ferrocenium test cell. This value was significantly higher than the 5.7% measured for similarly doped commercial n-GaAs wafers. Spectral response experiments showed that the higherperformance of CSVT n-GaAs films relative to the commercial wafers was due to longer minority carrier diffiasion lengths (L_D), up to 1,020 nm in the CSVT films compared to 260 rmi in the commercial "-GaAs wafers. Routes to improve the performance of CSVT GaAs and the implications of these results for the development of scalable GaAs-based solar energy conversion devices arediscussed.