Powder Synthesis and Bulk Crystal Growth of Gallium Nitride

The primary goal of Phase I work is to demonstrate the feasibility of synthesizing gallium nitride (GaN) powder. Secondarily, this powder will be used to grow high-purity single crystals of GaN from a liquid GaN phase. This would be accomplished using a proprietary variation of the skull melting technique. Since GaN demonstrates peritectic-type decomposition at atmospheric pressure, the entire skull melting apparatus will be operated at pressures sufficient to produce congruent melting of GaN. This technique is different from the Polish technique, where superheated gallium is reacted with extremely high pressure nitrogen to produce gallium nitride. In the first phase of the program, we will use a pilot hot mill to synthesize the gallium nitride powder. Once ample GaN powder has been synthesized, it will be used in a patent-pending apparatus to grow single crystals of GaN from a liquid GaN phase. Powder purity will be quantified using powder x-ray diffraction. Crystalline perfection will be determined using x-ray rocking curves. Micropipe and dislocation densities of crystals produced will be quantified using electron microscopy. This technique, matured in Phase II work, will provide BMDO with a low cost, high quality GaN wafer source. This patent-pending technology will provide large, low cost GaN single crystal wafers, to be used in the fabrication of GaN blue diodes and blue lasers, high temperature power FETs, and millimeter wave MMIC s. This technology is also applicable to AlN, SiC and YBCO superconductors. Corporate interest in this technology is very high, with Hewlett Packard, SDL, Xerox, CREE Research, Northrop Grumman, and Dow Chemical showing interest and some initial support.