Abstract: A physical vapor transport (PVT) apparatus suitable for growing SiC boules comprises a crystal growth chamber (with a defined central vertical axis), a sealed crucible containing sublimation source material and including a seed fixture disposed in an offset position with respect to the central vertical axis of the apparatus, and a heat source disposed to surround the crystal growth chamber. The heat source is configured to raise the temperature within the sealed crucible such that the source material vaporizes and deposits on the seed wafer. The offset position of the seed fixture creates a radial temperature gradient across an exposed surface of the seed as the crystal boule is grown.

Abstract: A crucible is provided that is thermally stable at high temperatures and is suitable for use in the growth of large, bulk AlN, AlxGa1-xN or other nitride single crystals. The crucible is comprised of specially treated tantalum. During the initial treatment, the walls of the crucible are carburized, thus achieving a crucible that can be subjected to high temperatures without deformation. Once the carburization of the tantalum is complete, the crucible undergoes further treatment to protect the surfaces that are expected to come into contact with nitride vapors during crystal growth with a layer of TaN. If the crucible is to be used with a graphite furnace, only the inner surfaces of the crucible are converted to TaN, thus keeping TaC surfaces adjacent to the graphite furnace elements. If the crucible is to be used with a non-graphite furnace, both the inner and outer surfaces of the crucible are converted to TaN.

Abstract: A crucible is provided that is thermally stable at high temperatures and is suitable for use in the growth of large, bulk AlN, AlxGa1-xN or other nitride single crystals. The crucible is comprised of specially treated tantalum. During the initial treatment, the walls of the crucible are carburized, thus achieving a crucible that can be subjected to high temperatures without deformation. Once the carburization of the tantalum is complete, the crucible undergoes further treatment to protect the surfaces that are expected to come into contact with nitride vapors during crystal growth with a layer of TaN. If the crucible is to be used with a graphite furnace, only the inner surfaces of the crucible are converted to TaN, thus keeping TaC surfaces adjacent to the graphite furnace elements. If the crucible is to be used with a non-graphite furnace, both the inner and outer surfaces of the crucible are converted to TaN.