GROWTH AND CHARACTERIZATION OF GAN THIN-FILMS BY MAGNETRON SPUTTER EPITAXY

Single crystal epitaxial gallium nitride films on GaN buffer layers we re grown on (0001) sapphire using magnetron sputter epitaxy. The films were characterized using x-ray diffraction, photoluminescence, scanni ng electron microscopy and transmission electron microscopy. In the la yers investigated thus far, the optimum buffer layer had a thickness o f 500 Angstrom at a growth temperature of 550 degrees C, while the opt imum growth temperature range for the active GaN epilayer was found to be 900 degrees C-950 degrees C. The growth rates for the buffer layer and GaN epilayer were 0.2 and 0.35 mu m/h, respectively. In general, photoluminescence studies showed emission from a broad defect band cen tered around 2.4 eV and a strong exciton peak at 3.48 eV. The exciton/ defect intensity ratio was strongly dependent on crystal quality at co nstant excitation intensity, The transmission electron microscopy stud ies revealed highly epitaxial GaN films, showing a kind of columnar gr owth structure, GaN films grown at 950 degrees C appeared to have the best structural quality. (C) 1998 American Vacuum Society. [S0734-2101 (98)08702-8].