Self-powered ultraviolet detectors may find application in aviation and military fields. Here we demonstrate a self-powered asymmetric metal-semiconductor-metal (MSM) deep ultraviolet (DUV) detector with an Ni/Al electrode contact to AlN, and a photoelectric response current increase from dark current (Id) 2.6 × 10-12 A to 1.0 × 10-10 A after UV illumination (Ip) at 0 V bias. To further improve device performance, trenches are etched in AlN, and the Ni/Al electrodes are deposited in trenches to form a three-dimensional MSM (3D-MSM) structure. The improved performance is attributed to the stronger electric field from the asymmetric electrode and a shorter carrier migration path from the 3D-MSM device configuration. Our work will promote the development and application of DUV self-powered devices.