Ultraviolet (UV) radiation, which covers the electromagnetic spectrum from 400 to 10 nm, can be divided into four subdivisions: UVA (320–400 nm), UVB (280–320 nm), UVC (200–280 nm), and VUV (vacuum UV, 10–200 nm). The sun is the primary source of UV light, and UVC light it typically absorbed by the ozonosphere when it passes through the atmosphere. Thus, no UVC photons exist naturally within the Earth’s atmosphere. Therefore, the UVC solar spectrum is also called the solar-blind UV waveband. This feature ensures that the detection of solar-blind UV photon signals within the Earth’s atmosphere is not affected by background radiation from sunlight, which gives the solar-blind UV detecting potential applications in early missile threat warning and tracking, environmental monitoring, engine monitoring, flame detection and monitoring, non-line-of-sight communications, etc.

Group-III nitride semiconductors exhibit superior properties, such as a wide energy bandgap, large thermal conductivity, high carrier mobility, small dielectric constant, strong anti-radiation ability, and good chemical stability. Due to these superior properties, III-nitride semiconductors can be applied in extreme environments, solid-state lighting and displays, short-wavelength lasers, and optical detection. III-nitride semiconductors primarily include GaN, AlN, and InN along with their ternary and quaternary alloys AlGaN, InGaN, and AlGaInN. Among these materials, the AlGaN ternary alloy semiconductor can tune its bandgap in the range of 3.4–6.2 eV by changing the Al component, covering the UVA, UVB, and UVC wavelength bands of 200–365 nm. Additionally, AlGaN exhibits a high specific detectivity approximately 1012 cm Hz1/2 W−1. Based on these outstanding optoelectronic characteristics, AlGaN ternary alloys exhibit marked advantages in promoting the evolution of UV photodetectors (PDs), particularly in fabricating intrinsic solar-blind UV detectors.