Development and Progress in Bulk c-Plane AlN Single-Crystalline Template Growth for Large-Area Native Seeds

Abstract

28-mm diameter free-standing AlN substrates were obtained from single crystalline templates grown hetero-epitaxially on (0001) SiC substrates by the sublimation method. The grown template crystals have fairly high structural quality with X-ray rocking curve FWHM values of 120 and 200 arcsec for symmetric and asymmetric reflections, respectively and an average etch pit density of about 5×10 5 cm -2 . In Raman spectroscopy, the E 2 (high) phonon mode peak FWHM is 18 cm -1 and its position shift shows a very low tensile strain of ∼1.5×10 -4 in the crystals. The presence of Si and C impurity-related local vibrational modes is observed. These impurities might be responsible for lowering the optical absorption band edge to 4.3 eV. Homo-epitaxial growth of 5-mm-thick bulk crystals, using 10 mm diameter seeds prepared from these templates demonstrates their suitability as native seeds for further growth.