Selective Growth of AlGaN-Based p-i-n UV Photodiodes Structures

Al_0.25Ga_0.75N ultraviolet (UV) p-i-n photodiodes (PDs) with top and inverted p-layer structure are created by selective-area growth on a GaN template layer. All PDs exhibit typical zero bias peak responsivity at 310 nm and the UV-to-visible (310/400 nm) spectral rejection ratio is greater than three orders of magnitude. In contrast to conventional AlGaN-based p-i-n photodiodes, the inverted devices with low-resistivity n-type AlGaN top-contact layers exhibit a nearly flat spectral response at the short wavelength regions (210-310 nm). The proposed device structure can achieve solar-blind, AlGaN/GaN-based p-i-n PDs with high-aluminum content and reduced tensile strain due to the lattice mismatch between AlGaN and GaN layers.