Effect of buffer layer growth temperature on epitaxial GaN films deposited by magnetron sputtering

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Epitaxial GaN films were deposited by reactive sputtering of a GaAs target in 100 % nitrogen at 700 °C on ZnO buffer layers grown at different substrate temperatures over sapphire substrates. High resolution X-ray diffraction measurements and the corresponding analysis show that the growth temperature of buffer layers significantly affects the micro-structural parameters of GaN epilayer, such as lateral coherence length, tilt and twist, while the vertical coherence length remains unaffected. The optimum substrate temperature for buffer layer growth has been found to be 300 °C. High epitaxial quality GaN film grown on such a buffer layer exhibited micro strain of 1.8×10−4 along with screw and edge type dislocation densities of 7.87×109 and 1.16×1011, respectively.