Sublimation epitaxy of AlN layers on 4H-SiC depending on the type of crucible

Epitaxial layers of aluminum nitride ≤335 μm thick have been grown at temperatures of 1900 and 2100 °C on 10×10 mm2 (0 0 0 1)-oriented α(4H) silicon carbide (SiC), with growth times of 1 and 4 h, via sublimation-recondensation in a RF-heated graphite furnace. The source material was polycrystalline AlN. The sublimation process was performed in three types of graphite (C) crucible: C1, C2 with inner diameters of 35 and 51 mm, respectively, and C3 with the same inner diameter as C1, but coated with a layer of TaC. The surface morphology reflects the hexagonal symmetry of the substrate, suggesting an epitaxial growth for samples grown in C1 and C3 crucibles for all growth conditions. The same symmetry is observed for AlN layers grown in the C2 crucible, but only at 2100 °C. X-ray diffraction analyses confirm the epitaxial growth of AlN samples with the expected hexagonal symmetry. A high-resolution X-ray diffractometer was used to assess the quality of the single crystals. A full width at half maximum of 242 arcsec was achieved for an AlN layer grown in the crucible coated with TaC.