We investigated the possibilities of vapour phase epitaxy in an open tube chloride system for thick GaN film deposition on sapphire substrates. The methodes of the buffer layer deposition were proposed and developed. The methods of fast ( up to 100 microns / hour ) was developed. Parameters of good quality gallium nitride epitaxy were obtained.
To determine the quality of fast grown epitaxial layers we used X-ray diffraction and photoluminescence measurements. The halfwidth of the rocking curve for the best samples was equal to 4-6 minutes. Luminescense spectrum ( T=77K ) had a maximum near 3.46 eV. A signal in the visible wavelength range was hardly observed. Polished layers were transparent.
A special initial treatment of the substrates allowed us to separate thick ( up to 300 micron ) epitaxial gallium nitride layers from sapphire. It was shown that it is possible to use separated films for homoepitaxy of GaN.