Defect effect on the performance of nonpolar GaN-based ultraviolet photodetectors

The anisotropy of GaN(11-20) makes it possible to fabricate polarized ultraviolet (UV) photodetectors (PDs) for applications in fields such as remote sensing and airborne astronomical navigation. The defect density has a significant effect on the performance of GaN(11-20)-based UV PDs. However, the mechanism through which different defects and their densities affect the performance of these devices is unclear. Therefore, in this work, we investigated the mechanisms of the screw or mixed dislocation, edge dislocation, and basal stacking fault (BSF) densities affecting the dark current, responsivity, and response time of GaN (11-20)-based PDs, respectively. We observed that the screw or mixed dislocation increased the dark current mainly through reducing the Schottky barrier height and forming leakage current, whereas the edge dislocation and BSF decreased the responsivity by reducing the electron mobility. Furthermore, all the three types of defects increased the response time through forming traps to recombine the holes with electrons and thus delaying the escape of carriers. These results are highly significant for developing nonpolar GaN-based UV PDs.