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 μm, 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 × 1015 ∼ 9.0 × 1015 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 °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.

Graphical abstractThe penetration depths of high-energy deuterium in GaN film were investigated using micro-Raman scattering spectroscopy. High-energy deuterium irradiation decreased the free carrier concentrations in GaN film, which were estimated by monitoring the QLO vibrational mode frequency. The empirical penetration depths of 5 MeV and 10 MeV deuterium were approximately 120 and 240 μm, respectively, where the carrier concentrations decreased as compared with pre-irradiated samples. After thermal annealing treatment, the reduced free carrier concentrations recovered up to similar level of the original values for 5 MeV, while partially recovered for 10 MeV.Figure optionsDownload full-size imageDownload as PowerPoint slide