Sublimation growth of 2 inch diameter bulk AIN crystals

The technology of sublimation growth of 15 mm diameter bulk single AIN crystals is scaled to grow similar 2-inch diameter crystals. The best results are currently achieved with the two-stage technique including 1) seeding and initial growth of 2-3 nun thick single-crystal AIN layers on 2-inch diameter 6H-SiC wafers in pre-carbonized Ta crucibles in graphite equipment and 2) growth of bulk AIN crystals on the above AIN layers in tungsten crucibles and equipment. The initial AN layers prove of good crystallographic quality but may contain up to 6 at.% of Si impurities. The eventual bulk AN crystals consist of about 40 mm diameter round single-crystal core and polycrystalline rim. No impurities in concentration higher than 0.01 at.% are found in. the bulk crystals. The bulk AIN crystal may be separated from the initial AN layer to use the latter repeatedly for growth of a new crystal. Such "secondary" crystals were found to be semi-insulating.