Abstract
Solar-blind ultraviolet (UV) photodetectors (PDs) have attracted tremendous attention in the environmental, industrial, military, and biological fields. As a representative III-nitride material, AlGaN alloys have broad development prospects in the field of solar-blind detection due to their superior properties, such as tunable wide bandgaps for intrinsic UV detection. In recent decades, a variety of AlGaN-based PDs have been developed to achieve high-precision solar-blind UV detection. As integrated optoelectronic technology advances, AlGaN-based focal plane arrays (FPAs) are manufactured and exhibit outstanding solar-blind imaging capability. Considering the rapid development of AlGaN detection techniques, this paper comprehensively reviews the progress on AlGaN-based solar-blind UV PDs and FPAs. First, the basic physical properties of AlGaN are presented. The epitaxy and p-type doping problems of AlGaN alloys are then discussed. Diverse PDs, including photoconductors and Schottky, metal–semiconductor–metal (MSM), p-i-n, and avalanche photodiodes (APDs), are demonstrated, and the physical mechanisms are analyzed to improve device performance. Additionally, this paper summarizes imaging technologies used with AlGaN FPAs in recent years. Benefiting from the development of AlGaN materials and optoelectronic devices, solar-blind UV detection technology is greeted with significant revolutions.
Highlights
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
Considering the materials used in avalanche photodiodes (APDs), high-Al-content AlGaN APDs are typically prepared on AlN/sapphire templates, and the material quality and performance of the fabricated devices are better than those used on GaN templates
The spontaneous and piezoelectric polarization in GaN-based semiconductors can introduce an internal electric field up to several MV/cm, which is of the same order of magnitude as the avalanche breakdown electric field in the multiplication region of AlGaN APDs
Summary
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 device exhibited a high detectivity, which exceeded 2.6 × 1012 cm Hz1/2 W−1, and a low noise power density below 3 × 10−29 A2/Hz at 10 kHz. Sang et al.[166] proposed an AlGaN-based solar-blind PD (Fig. 10a, b) with back illumination and used Ni/Pt Schottky contacts to reduce the leakage current.
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