Ultraviolet photodetectors using transparent gate AlGaN/GaN high electron mobility transistor on silicon substrate

Abstract

In this paper, UV photoconductivity of a transparent gate AlGaN/GaN high electron mobility transistor (HEMT) on a Si substrate is demonstrated. The transparent gate enables the HEMT to standby under pinch-off conditions for operation as a photodetector. Therefore, the device can overcome the drawback of high standby-current in conventional metal gate field-effect transistor (FET)-based photodetectors without sacrificing its high responsivity. A negative threshold-voltage shift of -0.25 V and a significant drain-current increase over two orders of magnitude were observed under UV-light irradiation condition from the surface-side. A high responsivity of 2.0 × 105 A/W at 360nm with a low leakage current of 3 × 10-6 A/mm was simultaneously achieved. These experimental results were in agreement with the models for generation of a photo carrier and its transportation in a heterostructure. © 2013 The Japan Society of Applied Physics.