Homoepitaxial seeding and growth of bulk AlN by sublimation

AlN boules, 35 rum in diameter and up to 25-mm long, were grown on TaC crucible lid in an inductively heated reactor. The growth rates range between 100 and 300 mu m/h. The boules grown on TaC show a columnar structure mostly composed of < 0 0 0 1 > grains. The largest grains (4-5 mm in diameter) were sliced and used for subsequent growth runs. Successful epitaxial seeding and growth on the starting AlN wafer was demonstrated and confirmed by electron back-scatter diffraction (EBSD) measurements. Crystals were grown on both Al and N surfaces of the seeds up to a maximum diameter of about 9 mm so far. Formation of oxy-nitride layers, very detrimental to the further AlN deposition, could be avoided when starting from pre-sintered source powder. Secondary ion mass spectroscopy (SIMS) measurements on axial cuts revealed a relatively low oxygen content, with variable distribution along the growth direction (290ppm near seed, 100ppm near external surface). (C) 2007 Elsevier B.V. All rights reserved.