Ultranarrow Band UV Detection in GaN with Simple Device Architecture

Abstract

An ultranarrow‐band ultraviolet (UV) GaN detector with a simple device architecture is presented. The device displays an ultranarrow band response centred at 366 nm with only ≈5 nm width, a UV–visible rejection ratio of >2 × 103, and detectivity of 1.3 × 1010 Jones at room temperature. The device is tested over a wide temperature range where the maximum response is recorded at 200 K. Temperature dependence of device response is explained by considering the thermal activation of shallow donors in low‐temperature regime and the establishment of thermal equilibrium of the donor level with conduction band at elevated temperatures. Moreover, the device displays three orders UV‐to‐visible rejection ratio over a wide temperature range of 150–350 K, showing great potential for narrowband UV detection even at elevated temperatures. Conventional and pump‐probe surface photovoltage spectroscopy measurements are performed with UV and infrared lasers to identify the electronic transitions associated with the narrowband response. It is understood that carrier excitation from valance band to shallow donor level in the interfacial depletion region is responsible for the observed behavior. The results presented here demonstrate an innovative methodology for achieving a stable and high spectrum‐selective UV photodetection without involving complex device architecture.