Low Temperature GaN Growth on Nitridated Sapphire Using Remote Plasma Enhanced Ultrahigh Vacuum Chemical Vapor Deposition

Abstract

GaN epitaxial thin films were grown on a nitridated sapphire at low temperature (550°C) using remote plasma enhanced ultrahigh vacuum chemical vapor deposition system and these films were investigated by Rutherford backscattering spectroscopy (RBS), X-ray diffraction(XRD) 8-rocking technique and the Ultraviolet-Visible-Nearinfrared (UV-VIS-NIR) absorption spectrum. The FWHJVI of the X-ray 9-rocking curve was about 0.4 degree using the (0002) reflection from the GaN layer with 5000Å thickness grown on the nitridated sapphire. An analysis of XRD and the UV-VIS-NIR absorption spectrum showed that the crystalline and optical qualities of GaN are dependent on the nitridation time of the sapphire even at low temperature when a plasma source is used for nitridation. This means that the density of protrusion, which is formed by a relaxation of the elastic energy caused by the lattice difference between the sapphire and Al_xO_1-xN, with the sapphire nitridation time plays a key role in the crystalline and optical properties of grown GaN films. The RBS channeling data and the FWHM value of the 9-rocking curve for GaN₍₀₀₀₂₎ also indicated that the truncated hexagonais are tilted towards each other. These results showed that the GaN epitaxial film can be successfully grown on nitridated sapphire by RPE-UHVCVD even at low temperature.