Photoelectrochemical Properties of the p−n Junction in and near the Surface Depletion Region of n-Type GaN

Photoelectrochemical water splitting is expecting a new energy source to produce hydrogen from water. The photoilluminated electrode using a uniform semiconductor single crystal has been well analyzed, but the effect of that using a structural semiconductor is still obscure. The properties of one of the structural semiconductors with a p−n junction in and near a depletion region were investigated using the samples with thin p-type layers on n-type GaN in this article. The properties were also evaluated by the calculation based on the Poisson equation. Not only the band-edge energy of a semiconductor at the semiconductor−electrolyte interface but also the length of the depletion region and the band-edge energy profile affected the photocurrent density from the evaluation. The effect of the energy profile of the depletion region is also discussed.