Development of Thermally Stable, Solar-Blind Deep-Ultraviolet Diamond Photosensor

Abstract

A thermally stable, deep-ultraviolet (DUV) photodiode is developed by using tungsten carbide (WC) Schottky and Ti/WC Ohmic contacts for boron-doped homoepitaxial p-type diamond epilayer. Thermal annealing at temperatures lower than 550°C improves the rectifying current-voltage characteristics of the photodiode, resulting in a dramatic enhancement of DUV responsivity at 220 nm by a factor of 3×10⁴. A discrimination ratio between DUV and visible light is measured to be as larger as 10⁵ at a reverse bias as small as 2 V and almost constant after annealing at 550°C for 2.5 h. Development of the thermally-stable WC-based Schottky and Ohmic contacts opens up possibility for stable operation of diamond photosensor at high temperatures.