Enhanced Photoresponse of Single GaN Microwire Ultraviolet Photodetectors by Heteroepitaxial AlN Coating Layer

Core–shell heterojunction structure is a feasible approach to optimize the optoelectronic performance of devices by combining the advantages of different materials. In this work, GaN/AlN core–shell heterojunction microwire‐based photodetector (PD) has been fabricated, and appropriate epitaxy growth of AlN can improve the performances of PDs. Compared with pure GaN microwire device, the enhanced responsivity, sensitivity, detectivity, and external quantum efficiency value of 4160 A W−1, 1.88 × 107%, 3.93 × 1012 Jones, and 4.07 × 106% are obtained with 5 nm thick AlN. Meanwhile, a rise/decay time of 25/16 ms is possessed. In addition, the responsivity and detectivity are increased with an acceptable decrease in sensitivity when the exciting light intensity decreases. The effective advances of PDs are benefited from the increased Schottky barrier height, the built‐in electric field that promotes the separation of photogenerated electron‐hole pairs, and direct heteroepitaxial growth high crystal quality GaN/AlN core/shell structure, which will effectively passivate the surface of GaN microwire by covering AlN. This study sheds some light on fabricating high‐performance microwire‐based PDs. The high‐performance GaN/AlN core–shell heterojunction microwire UV photodetector (PD) has been fabricated by direct heteroepitaxial growth, and results indicate that an appropriate thickness of AlN can effectively enhance its performance compared to pure GaN microwires PDs. These can be attributed to the increased Schottky barrier height, and effective passivation of GaN surface states by AlN.