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Growth of AlN single crystals by modified PVT

Growth of AlN single crystals is achieved by physical vapor transport (PVT) in the reverse cone tungsten crucible, which is induction-heated, for obtaining proper sublimation rate and ensuring effective heat and mass transport. In the experiment, there is a little hole at the center of crucible lid where the temperature is lower than the periphery, and there is a tungsten cover on the lid. A self-seeded AlN single crystal is grown due to the anisotropic growth property of AlN crystals and limitation of the hole. During the following growth, the crystal as a seed becomes a large size and high quality single crystal. By modified PVT, separate AlN single crystals with diameters of larger than 2mm on the crucible lid have been obtained successfully for the first time.