Numerical investigations into the impact of substrate defects on a grooved GaN-based ultraviolet phototransistor with an AlGaN polarization gate

Abstract

In this work, we propose defect-related models for a grooved GaN/AlxGa1−xN/GaN UV phototransistor with an AlGaN polarization gate. The AlGaN polarization gate is set under the absorptive layer. With the developed models, we find that without the AlGaN polarization gate, the donor-type traps increase the dark current. In contrast, the electron trapping effect by acceptor-type traps reduces the dark current. Moreover, the AlGaN polarization gate helps deplete the electrons under the grooved region, which makes the dark current further suppressed. We also investigate the influence of the Al composition and the polarization level for the AlGaN polarization gate on the carrier transport, the dark current, and the photocurrent. Meanwhile, we report that the grooved depth plays an important role in reducing the background channel electron concentration, and the channel under the grooved region can be effectively closed by the AlGaN polarization gate when the grooved depth is properly set.