Abstract
Light illumination of a gallium nitride photoelectrode creates separate electron-hole pairs that drive water oxidation and CO2 reduction reactions. Here, we show enhanced photocurrent in an AlGaN/GaN device that consists of an unintentionally doped (uid-) AlGaN photoabsorption layer and an n(+)-GaN electrical-conduction layer. The production rate of formic acid by CO2 conversion in the uid-AlGaN/n(+)-GaN photoelectrode is about double that in the uid-GaN/n(+)-GaN device. This improvement is most likely due to the effect of internal bias in the uid-AlGaN layer generated by the polarization effect, which improves electron-hole separation. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4729298]