An Anomalous Gain Mechanism in GaN Schottky Barrier Ultraviolet Photodetectors

The gain mechanism in GaN Schottky barrier ultraviolet photodetectors is investigated by focused light beam. When the incident light illuminates the central region of the Schottky contact electrode, the responsivity changes very little with the increase of reverse bias voltage. However, when the incident light illuminates the edge region of the electrode, the responsivity increases remarkably with the increase of reverse bias voltage, and the corresponding quantum efficiency could be even higher than 100%. It is proposed that the surface states near the edge of the electrode may lead to a reduction of effective Schottky barrier height and an enhancement of electron injection, resulting in the anomalous gain.

National Natural Science Foundation of China 60836003 60776047605060016047602160576003National Basic Research Program of China 2007CB936700 National High Technology Research and Development Program of China 2007AA03Z401 Supported by the National Natural Science Foundation of China under Grant Nos 60836003, 60776047, 60506001, 60476021 and 60576003, the National Basic Research Program of China under Grant No 2007CB936700, and the National High Technology Research and Development Program of China under Grant No 2007AA03Z401.