Selective Area Epitaxy of GaAs Microstructures by Close-Spaced Vapor Transport for Solar Energy Conversion Applications

Close-spaced vapor transport is a plausibly low-cost, high-rate method to grow HI-V materials for photovoltaic and photoelectrochemical device applications. We report the first homoepitaxial growth of GaAs microstructures on (100)- and (111)B-oriented GaAs substrates using patterned SiOx and Al2O3 masks and show that the resulting microstructured GaAs is an efficient semiconductor absorber for photovoltaic and photo-electrochemical applications. Cross-sectional transmission electron microscopy reveals an unusually low density of twin-plane defects in the (111)-oriented microstructures and the occurrence of stacked twin-plane defects in the (100)-oriented microstructures. Nonaqueous photoelectrochemical measurements show similar short-circuit currents of 9.7 and 9.1 mA cm(-2) for (100)- and (111)-oriented microstructures, respectively, with promising external quantum efficiencies. Together, the low twin density and good electronic properties indicate that micro- or nanostructures grown by selective area epitaxy in close-spaced vapor transport are promising for device applications that take advantage of their three-dimensional structure.