The microstructural and luminescent properties of sputtered GaN thin films preiiradiated and γ-ray irradiated were systematically investigated. Analytical results revealed that the increasing doses of γ rays could enhance the occurrence of more nitrogen vacancies, which not only created a prominent deep level luminescence but also destroyed the crystallinity of GaN thin films. For low dose of γ-ray irradiation [≦4 Mrad (GaN)], evidence showed that by raising the irradiation dose, more associated Ga–H complexes would be effectively promoted, yielding an enhanced yellow band emission. However, for high dose of γ-ray irradiation [>4 Mrad (GaN)], further higher doses of γ rays could lead to the dissociation of Ga–H complexes in GaN samples, resulting in a repressed yellow band emission. From both the Fourier transform infrared spectroscopy and yellow band emission results, it is strongly suggested that Ga–H complexes in the vicinity of N most probably act as the origin of yellow band emission in GaN material.
The structural and optical properties of rf magnetron-sputtered GaN thin films on p ϩ -Si substrates have been accessed as a function of rapid thermal annealing ͑RTA͒ temperatures from 800 to 1000°C. The evidence has revealed that higher RTA temperatures not only assist the GaN films in recrystallizing into stable hexagonal form but also enhance the near-band-edge emission of GaN films in the photoluminescence spectrum. Moreover, a deep electron trap (E t ) with activation energy E c ϪE t Х0.39 eV detected at the surface of higher-RTA-temperature-treated GaN films was asserted to be a nitrogen-vacancy-related defect that takes a defect-assisted-tunneling role in the forward conduction process of Au/GaN Schottky diode. The greater reverse leakage current and lower breakdown voltage are suggested to be due to the effects of a lower barrier height and higher ideality factor that occurred in the higher-RTA-temperature-treated samples.
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