Effect of growth temperature on the properties of p-type GaN grown by plasma-assisted molecular beam epitaxy

p-type GaN films were grown at two different temperatures, 650 and 700°C, by plasma-assisted molecular beam epitaxy (PAMBE) using a radio frequency (RF) plasma source. High hole concentrations of the order of 10¹⁸ cm^-3 were achieved for both films without any post-growth treatment. For (0 0 0 2) diffraction from the p-type films grown at 700°C, the full-width at half-maximum (FWHM) of the double-crystal X-ray rocking curve was 7.8 arcmin, the smallest ever reported for p-type GaN films grown on sapphire substrates. The room-temperature photoluminescence (PL) measurements on both films showed that band edge emission at 365 nm dominated the PL spectra of the films grown at 700°C, while emission at 413 nm, associated with deep Mg complexes, dominated those of the films grown at 650°C. The films grown at 700°C showed better crystalline quality and optical properties than those grown at 650°C.