The structural and optical properties of rf magnetron-sputtered GaN thin films on p(+)-Si substrates have been accessed as a function of rapid thermal annealing (RTA) temperatures from 800 to 1000 degrees 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-E(t)congruent to 0.39 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.