Preparation of GaN films on glass substrates by middle frequency magnetron sputtering

GaN films were deposited on glass substrates by the middle frequency magnetron sputtering method at low substrates temperatures. X-ray diffraction (XRD) intensity and full-width at half-maximum (FWHM) values of the films were strongly influenced by the composition of (Ar+N2) mixture gas and the negative bias voltages. Optical band gaps deduced from absorption plots show a decrease trend with increasing bias voltages. The unintentionally doped films deposited under optimal conditions were normally n type with a typical carrier concentration of 1.92×1017/cm3 and Hall mobility of 49 cm2/V s. Two photoluminescence emission peaks appear at 3.30 and 3.36 eV at temperatures below 100 K, and the origin of these two peaks can be attributed to excitons bound to structural defects.