Low Temperature Growth of GaN Epitaxial Layer on Sapphire (0001) Substrate by Laser Molecular Beam Epitaxy Technique

GaN epitaxial layers have been grown on sapphire (0001) substrate by laser molecular beam epitaxy. The Ga and N fluxes have been optimized for a good quality, smooth surface GaN layer growth by suitably adjusting the laser power and frequency. It is found that the moderate laser energy with high frequency up to 45 Hz yields more uniform Ga flux for the growth. Similar to conventional MBE, the N-rich growth condition produced rough surface GaN layers while flat surface GaN was obtained under slightly Ga-rich condition. The effect of growth temperature in the range 300–750 °C on the structural properties of the grown GaN layers has been studied. The (0002) plane x-ray rocking curve full width at half maximum (FWHM) of GaN epilayers has been found to decrease dramatically with increasing growth temperature. A narrow x-ray rocking curve value of about 245 arcsec has been achieved for GaN (0002) plane reflection for the epilayers grown in the range of 500–600 °C, which is about 150 °C lower than the conventional MBE growth.