Micro-Raman measurement of high-energy deuterium irradiated GaN

Micro-Raman spectroscopy was used to examine the changes in the structural and electrical properties of GaN films exposed to high-energy deuterium irradiation. The locations of the larger structurally damaged regions, at irradiation energy of 5 MeV and 10 MeV, were determined by monitoring the variations of the quasi-longitudinal optical phonon frequency. The empirical penetration depths after 5 MeV and 10 MeV deuterium irradiation were approximately 120 and 240 mu m, respectively, where the carrier concentrations was lower than that of the pre-irradiated samples. Defect clusters were generated in GaN crystal through collisions with lattice atoms, and acted as carrier traps. The carrier concentrations of the GaN sample after deuterium irradiation, which were derived from the quasi-longitudinal optical (QLO) Raman shifts, ranged from 5.5 x 10(15) similar to 9.0 x 10(15) cm(-3). The reduced free carrier concentration of the sample irradiated at 5 MeV was recovered almost to its pre-irradiation values by annealing at 900 degrees C, whereas only partial recovery was observed in the sample irradiated at 10 MeV. This study provides insights into the degradation mechanism caused by high-energy particle irradiation and the long-term reliability of GaN-based electronic devices. (C) 2012 Elsevier B.V. All rights reserved.