Annealing of GaN/ZnO/Si films deposited by pulsed laser deposition

ZnO buffer layers were used in the fabrication of GaN films by pulsed laser deposition (PLD) in order to improve the initial nucleation and growth of GaN films when they are annealed in ammonia ambience at different temperatures. The crystalline quality, composition and surface morphology of the films were characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared (FTIR) analysis and atomic force microscopy (AFM). Through the analyses of measured results, a conclusion can be drawn that the crystalline quality of GaN films deposited on ZnO buffer layers is much higher than that of those deposited directly on Si substrates with the volatilization of ZnO. The volatilization of ZnO buffer layers gives the grains of GaN more chances to move and form Ga-N bonds at high temperatures. The annealing temperature markedly affects the preparation of GaN films and the optimum annealing temperature is 950 degrees C under our experimental conditions.