In this research, an InGaN-based photoanode with a broadband light-absorption range from ultraviolet to green, patterned by imprint lithography and branched by ZnO nanowires, has been applied to water splitting. Over the solar spectrum range, the absorbance increases due to the scattering effect of the micro-structure compared to that of flat surface InGaN, which reaches a maximum of over 90% at 380 nm as ZnO nanowires are further employed in this novel photoanode. Consequently, the induced photocurrent density of the InGaN photoanode with a domelike structure and ZnO nanowires on the surface shows a remarkable enhancement of seven times that of the one with a flat surface. Further investigation indicates the wet-etching process for defect removal has an essential impact on photocurrent efficiency. This design demonstrates an innovative approach for water splitting.