Evolution in the development of photodetectors: From ultraviolet to terahertz

Abstract

The paper presents the evolution in the development of photodetectors over a wide spectral range, from the ultraviolet to the infrared, over the last two decades. Technological advancements have led to the evolution of detector architectures that enhance device sensitivity, improve frequency response rates, reduce noise levels, and increase gain bandwidth. Initially, the key mechanisms of detector operation are briefly discussed, including those found in the new generation of low-dimensional solid (LDS) photodetectors. More attention is paid to the advantages and disadvantages of the new generation of materials used in active areas of photodetectors. In the case of ultraviolet (UV) photodetectors, AlGaN and Ga2O3 are extremely promising due to their low complexity and weight, while offering good sensitivity and robustness. Also, UV photodetector concepts inspired by new device architectures based on LDS materials are described. Due to the large number of published papers, visible-range photodetectors are treated rather marginally. Only the general development of their arrays is outlined. Among different types of infrared (IR) detectors, special attention is directed toward HgCdTe alloys, type-II superlattices, quantum wells, and lead salts. The performance of new emerging LDS photodetectors (mainly based on colloidal quantum dots and 2D materials) is compared with standard ones dominating the commercial market. This section of the article also covers hybrid infrared detector arrays, with particular emphasis on hybridization techniques, pixel scaling, thermal system optics, and signal readout electronics. An attempt was also made to describe the state of the new generation of IR focal plane arrays (FPAs) with LDS pixels. Finally, terahertz imaging arrays are discussed, with a focus on systems that operate at both room temperature and cryogenic temperatures. The challenges facing the implementation of LDS materials and the prospects for their development in terahertz imaging are also described.