Preparation of Bulk AlN Seeds by Spontaneous Nucleation of Freestanding Crystals

Freestanding AlN single crystals are grown in a RF-heated furnace by physical vapor transport (PVT). Three different growth regimes with growth temperatures between 2080–2200°C result in different crystal habits and very high structural quality. The Rocking curves show FWHM < 21 arcsec in the 0002 and 101̄0 Reflection on the as-grown facets. Isometric AlN crystals with sizes up to 10 × 10 × 12mm3show a zonar structure consisting of a yellowish core area which is grown on the N-polar (0001̄) facet and a nearly colorless edge region grown on prismatic {101̄0} facets. In the two growth zones nearly the same C concentrations but different amounts of O and Si are measured by secondary ion mass spectrometry (SIMS). The yellowish core area show a very low defect density (EPD ⩽ 100 cm−2) and a higher deep UV transparency compared to the edge region.