A comparison of aluminum nitride freely nucleated and seeded on 6H-silicon carbide

The crystal quality, vibrational and luminescence properties of AlN crystals prepared by the sublimation-recondensation method with free nucleation on the crucible walls or seeded growth on 6H-SiC wafers were compared. Freely nucleated needles and platelets exhibited near-band-edge cathodoluminescence, narrow Raman peak widths, and a relatively low dislocation density as revealed by synchrotron white-beam x-ray topography. In contrast, thick films deposited on on-axis, (0001) 6H-silicon carbide wafers exhibited luminescence only at 3.5 eV, had much broader Raman peak widths, and a mosaic crystal structure.