An UV photodetector includes: a substrate, a template layer formed on the substrate, an intrinsic AlGaN layer formed on the template layer, a first n-type AlGaN layer and a second n-type AlGaN layer formed on the intrinsic AlGaN layer side-by-side and separated by a gap, wherein the gap exposes the intrinsic AlGaN layer. Another UV photodetector includes: an UV transparent substrate, an UV transparent template layer formed on the substrate, a first UV transparent n-type AlGaN layer formed on the UV transparent template layer, an intrinsic AlGaN layer formed on the first UV transparent n-type AlGaN layer, a second n-type AlGaN layer formed on the intrinsic AlGaN layer, and a p-type layer formed on the second n-type AlGaN layer.