Effect of minute compositional variations on the photoelectrochemical properties of InGaN/TiO2 heterostructure electrodes

We report on the growth of single crystalline InGaN nanostructures with minute compositional variation on sapphire at a low substrate temperature of 350 °C that shows good optical and electrical properties. We investigate the photoelectrochemical performance of InGaN with two different average In compositions (13 and 16%) and compare the properties by forming their heterostructures with TiO2 (InGaN/TiO2). A significant enhancement in photocurrent density has been observed by using the heterostructures with more In content, in comparison to the InGaN having the same In content and also with the heterostructure having lesser In content. Though the average In compositional difference is only 3%, the de-convoluted XRD (0002) curve shows significant change in one of the phases (In0.29Ga0.71N) with an increment in both indium composition (6%) and in the phase area, which results in the significant difference in photoelectrochemical properties. The transient photo response analysis shows that both samples are fast responsive, while the photocurrent density is significantly different with the fabrication of heterostructures. A suitable change in band diagram of the system is sketched, which shows the band bending enhances the separation and migration of the photogenerated carriers to the semiconductor/electrolyte interface, thereby the photocurrent density.