Ultralow Dark-Current and Superhigh Detectivity Ultraviolet Photodetector Based on Freestanding GaN Nanobelt Array

One-dimensional (1D) GaN nanostructures have attracted increasing attention due to their unique optical absorption and electrical transport characteristics. Herein, we demonstrate the preparation of a single-crystalline GaN nanobelt (NB) array with remarkable optical and carrier confinement property by combining top-down etching and epitaxial lift-off techniques. The peeled-off NB demonstrated lower nonradiative recombination and higher radiative recombination probability, which indicated the lees defects in the peeled-off NB. Based on the obtained high-quality GaN NB array, high performance ultraviolet photodetectors (UV PDs) with Ohmic contacts were fabricated. Under a low bias of 1.0 V, the representative PD shows a high responsivity >500 A W –1, a high detectivity of 3.08 × 10 16 Jones, and a fast response time at 325 nm. In particular, the PD exhibits extremely high light on/off ratio >10 8 . To our best knowledge, the obtained on/off ratio is the best result for 1D GaN based UV PDs, which is ascribed to the ultralow dark current caused by strong surface depletion of the released GaN NBs. This work provides a route for GaN NB preparation and transfer, which is conducive to develop functional devices such as GaN heterogeneous integrated devices and flexible devices.