Vertically Stacked Triple-Bands Metal-Semiconductor-Metal Structured-Whole Ultraviolet Photodetectors

In this work, to detect the whole ultraviolet (UV) wavelength band comprising UVA, UVB, and UVC, triple-band metal-semiconductor-metal (MSM)-structured UV photodetectors (UV-PDs) were fabricated and analyzed. The ZnO, TiO2, and Ga2O3 materials were utilized to detect UVA, UVB, and UVC, respectively. The vertically stacked Ga2O3/TiO2/ZnO films were deposited on sapphire substrates using a vapor-cooling condensation system. This deposition method effectively suppressed the undesired oxygen vacancies and defects existing in those deposited films to very low concentrations. As a result, the solar-blind performances of the resulting UV-PDs were achieved. Furthermore, to augment the sensing area and shorten optically induced carrier propagation distance, the inclined sidewalls of UV-PDs were engineered. The comparative performances of the triple-band MSM-UV-PDs without and with the inclined sidewalls were extensively measured and studied. This investigation revealed that the use of inclined sidewalls led to increased photoresponsivity and reduced switching times.