Growth and characterization of GaN thin films by magnetron sputter epitaxy

Abstract

Single crystal epitaxial gallium nitride films on GaN buffer layers were grown on (0001) sapphire using magnetron sputter epitaxy. The films were characterized using x-ray diffraction, photoluminescence, scanning electron microscopy and transmission electron microscopy. In the layers investigated thus far, the optimum buffer layer had a thickness of 500 Å at a growth temperature of 550 °C, while the optimum growth temperature range for the active GaN epilayer was found to be 900 °C–950 °C. The growth rates for the buffer layer and GaN epilayer were 0.2 and 0.35 μm/h, respectively. In general, photoluminescence studies showed emission from a broad defect band centered 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 constant excitation intensity. The transmission electron microscopy studies revealed highly epitaxial GaN films, showing a kind of columnar growth structure. GaN films grown at 950 °C appeared to have the best structural quality.