A Novel Growth Technique for Large Diameter AlN Single Crystal

78072S III-V nitride-based, high brightness, UV and visible light emitting diodes (LEDs) are of a great interest for general illumination, but the low light output efficiencies of current high brightness LEDs are still inadequate. A key material issue preventing the achievement of higher light output efficiency in LEDs is the poor crystalline quality of the nitride epitaxial layers that result from lattice-mismatched substrates. This project will develop a novel, physical vapor transport (PVT) technique to grow large diameter, high quality AlN bulk single crystals, which can be used as substrates for the growth of high quality nitride LED epitaxial layers. In Phase I, the PVT technique for AlN single crystal growth will be studied extensively in order to understand the effect of the crucible/insulation set-up, used for the PVT growth, on the quality of AlN crystal boules. In particular, protective TaC coatings on graphite crucibles will be fabricated and tested, a PVT AlN crystal growth process will be developed, defects and impurities in the AlN crystals will be characterized, and AlN crystal boules will be fabricated into wafers. Commercial Applications and Other Benefits as described by the awardee: Significant improvements in light output efficiences during the past decade have made GaN-based LEDs the most promising contender for future general illumination application. High brightness LEDs hold great promise for future general illumination applications because of their tremendous energy saving potential, long life time, compactness, and potential cost savings.