Polarization assisted self-powered GaN-based UV photodetector with high responsivity

Abstract

In this work, a self-powered GaN-based metal-semiconductor-metal photodetector (MSM PD) with high responsivity has been proposed and fabricated. The proposed MSM PD forms an asymmetric feature by using the polarization effect under one electrode, such that we adopt an AlGaN/GaN heterojunction to produce the electric field, and by doing so, an asymmetric energy band between the two electrodes can be obtained even when the device is unbiased. The asymmetric feature is proven by generating the asymmetric current-voltage characteristics both in the dark and the illumination conditions. Our results show that the asymmetric energy band enables the self-powered PD, and the peak responsivity wavelength is 240 nm with the responsivity of 0.005 A/W. Moreover, a high responsivity of 13.56 A/W at the applied bias of 3 V is also achieved. Thanks to the very strong electric field in the charge transport region, when compared to the symmetric MSM PD, the proposed MSM PD can reach an increased photocurrent of 100 times larger than that for the conventional PD, even if the illumination intensity for the light source becomes increased.