Structural and composition analysis of GaN films deposited by cyclic-PLD at different substrate temperatures

GaN films were deposited by cyclic pulsed laser deposition (cyclic-PLD) at different substrate temperatures between 400 and 600 °C. Alignment of the films along the c-axis, grain size, roughness and conductivity increased with temperature. Surface elemental ratio N/Ga was determined by X-ray photoelectron spectroscopy (XPS) and was smaller for films deposited at higher temperature. A decrease of the resistivity of the films agreed with higher metallic (Ga) surface concentration. Bulk elemental ratio N/Ga, determined by Rutherford backscattering spectroscopy (RBS), was higher than the XPS ratio and showed a very small tendency to decrease with deposition temperature. At 600 °C, there was evidence of contamination of the films by oxygen probably resulting from diffusion from the sapphire (Al2O3) substrate. These results suggest that adjustments in the deposition conditions are needed in order to have high crystal alignment, large grain size and good N/Ga ratio.