Dislocation-related deep states induced by irradiation in HVPE n-GaN

Abstract

This paper deals with defects induced by proton irradiation in n-GaN. The samples were HVPE grown, irradiated with 24 GeV protons. DLTS was performed on both as-grown and irradiated samples with planar and normal collector configurations to evidence the dislocation effect. Two electron traps were identified in the as-grown material by both diode structures: trap EC1 (E_C – 0.19eV) and trap EC2 (E_C – 0.25eV), EC2 being the dominant one. Irradiation consistently affects the pre-existing levels in such a way so as their appearance strongly depends on the diode structure, hence on the region probed by DLTS.

This contribution focuses on the actual existence of two deep traps EC1 and EC2 emitting in GaN at low temperature and on the different nature of the deep levels associated to EC1 and EC2. Their filling kinetics was studied since we supposed that EC2 would be associated to extended defects, as already reported in literature. Indeed, the site density of EC2 logarithmically depends on the filling pulse width, demonstrating that this trap is definitely associated to extended defects. The trap EC1, on the contrary, exhibits the filling kinetics peculiar of point defects.