Photoluminescence changes in n-type GaN samples after photoelectrochemical treatment

Photoelectrochemical water splitting using semiconductors to produce hydrogen is a promising technique for converting sunlight to chemical energy. However, anodic photocorrosion occurs during the reaction even when n-type GaN, a chemically stable material, is used for the photo-illuminated working electrode. We previously demonstrated that the stability is related to the amount of Si doping used to make the GaN to be n-type. This means that, the surface damage after photoelectrochemical reaction depends on the amount of Si. We have now investigated the relationship between this surface change and the optical properties especially for the near band edge peaks. With the peak shift by the strain relaxation due to the surface change from smooth to rough, new peaks around 3.4 eV were observed after photoelectrochemical treatment. These new peaks are defect-related emission, which has been reported as Y _i lines.