Evaluation of high-performance, self-powered and wavelength-selective InGaN/GaN multiple quantum well UV photodetectors fabricated on sapphire substrate: Analysis of the influence of growth temperature

The impact of growth temperature (GT), in the range from 875° to 825°C, on the morphological, structural, electrical, and optical properties of InGaN/GaN multiple quantum well ultraviolet photodetectors (UV-PDs) is investigated. Lowering of GT is found to increase In composition in the well layers and deteriorates surface and crystalline quality as confirmed via atomic force microscopy, and X-ray diffraction analyses. Under suitable light, all the fabricated devices show outstanding photoresponse properties. The detector fabricated using the epilayer grown at 825 °C (PD-A) exhibits the lower value of open circuit voltage which is related to the incorporation of In composition upon decreasing of GT. Despite the high dark current, PD-A shows the larger short circuit current density under a 1-sun-intensity measurement due to enlarged sub-bandgap photons absorption, resulting in a significant enhancement in energy conversion efficiency. The photocurrent measurements suggest that PD-A has a relatively better performance compared to others (higher GT) because of its higher values of responsivity, detectivity, superior bias, and light power-dependent photo-electric characteristics. In addition, the time-dependent photo-response characteristics reveal that PD-A has a greater capability to monitor fast varying UV signals. Finally, the evaluated results imply that the performance of UV-PDs is intensely influenced by GT.