Progress in ultraviolet photodetectors based on II-VI group compound semiconductors

Ultraviolet (UV) photodetectors (PDs) have found widespread application in various fields, such as environmental protection, life sciences, secure communications, automated systems, and missile tracking, which renders UVPDs the most important component in modern optoelectronic devices and systems. In the past decade, a large number of UVPDs with various device structures and fast response speed have been reported. While most of the UVPD devices are usually assembled from Si and other semiconductor materials, II-VI group semiconductors (ZnS, ZnSe, etc.), which have a wide bandgap and high exciton binding energy, are regarded as potentially important candidates for high-performance UVPD application as well. In this review, we comprehensively discuss the basic concepts and operation mechanisms of UVPDs, which are key factors for rational comparison between different photodetectors. In addition, the main research status of UVPDs based on II-VI group semiconductors is reviewed. Some emerging techniques to optimize device performance are discussed as well. Due to the trade-off between the two key parameters of the responsivity and response time, the ultimate performance of some II-VI group semiconductor-based UVPDs remains inadequate. And then, the initial applications based on II-VI group semiconductor photodetectors are mentioned. Finally, the current challenges and future directions of II-VI group semiconductor-based UVPDs are outlined and discussed, and general advice for realizing novel high-performance photodetectors and their applications is given to provide a guideline for the future development of this fast-developing field.