Aluminum nitride single crystal is one of the promising materials for substrates of GaN-based laser diodes. However, its potential in some of this and other applications has been hampered by the lack of bulk single crystals. Growth of AlN single crystals by the sublimation method and other growth techniques has been investigated in several laboratories. We review the sublimation method for growth of AlN single crystal, prepared crystals by this technique and characterized them. The crystals are transparent and slightly yellow. They are needle-shaped with a hexagonal cross section, plate-shaped or needle-shaped with a rectangular cross section. Their widths of x-ray rocking curves is about 39 arcsec, with a full width at half-maximum, 203 arcsec and 12 arcsec, respectively. The orientation of AlN single crystal axis is sufficient for use in substrates for GaN-based diodes. The problems on the sublimation method for better and lager AlN single crystal were also reviewed.
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