Vacuum Ultraviolet Photodetector with Low Dark Current and Fast Response Speed Based on Polycrystalline AlN Thin Film

A metal–semiconductor–metal (MSM) vacuum ultraviolet (VUV) photodetector is realized on polycrystalline AlN film grown by molecular beam epitaxy. At a bias of 10 V, the dark current of the device is less than 120 fA and the VUV (185 nm) to Ultraviolet‐C (255 nm) rejection ratio is more than 10 3 . More interestingly, the polycrystalline AlN photodetector shows an ultra‐fast response speed with a 90%–10% decay time of ≈50 ns, which is much quicker than any other previously reported AlN VUV photodetectors. Furthermore, the device still maintains stability and repeatability at 473 K. This research shows that polycrystalline AlN photodetector has good photodetection performance, which will help advance the design and preparation of AlN‐based VUV photodetectors.