Vapor phase epitaxy of GaN using gallium tri-chloride and ammonia

GaN films with good crystalline quality are grown on sapphire by atmospheric pressure vapor phase epitaxy using gallium tri-chloride (GaCl ₃) and ammonia (NH ₃). Epitaxial growth is carried out over temperature and V/III-ratio ranges of 800-1000°C and 100-1000, respectively. Typical growth rate obtained is in the range of 5-20 μm/hr. The films grown below 925°C typically show three dimensional (island) growth, while above that temperature, continuous films are obtained. Films grown at 975°C with a V/III ratio > 300 exhibit a smooth surface. XRD analysis shows that the films are single crystal with hexagonal polytype. Strong band-edge photoluminescence is observed with a FWHM of 60 meV at room temperature and 25 meV at 77K. The results indicate that this simple growth technique is effective for growing high quality bulk GaN, which can be used as a substrate for subsequent epitaxy. In order to further improve the surface morphology, a preliminary experiment on GaN growth on a thin GaN buffer layer prepared by gas source MBE is also presented.