Growth of SiC and III–V nitride thin films via gas-source molecular beam epitaxy and their characterization

Abstract

Silicon carbide (SiC) and aluminum nitride (AlN) thin films have been grown on 6HSiC(0001) substrates by gas-source molecular beam epitaxy (GSMBE) at 1050°C. Step flow, step bunching and the deposition of 6HSiC occurred at the outset of the exposure of the (1 × 1) vicinal substrate surface to C 2 H 4 Si 2 H 6 gas flow ratios of 1, 2 and 10. Subsequent deposition resulted in step flow and continued growth of 6H films or formation and coalescence of 3CSiC islands using the gas flow ratio of one or the ethylene-rich ratios, respectively. The (3 × 3) surface reconstruction observed using the former ratio is believed to enhance the diffusion lengths of the adatoms, which in turn promotes step flow growth. Essentially atomically flat monocrystalline AlN surfaces were obtained using on-axis substrates. Island-like features were observed on the vicinal surface. The coalescence of the latter features at steps gave rise to inversion domain boundaries (IDBs) as a result of the misalignment of the Si C bilayer steps with the AlN bilayers in the growing film. The quality of thicker AlN films is strongly influenced by the concentration of IDBs. Undoped, highly resistive (10 2 Ω · cm) and Mg-doped, p-type (0.3 Ω · cm) monocrystalline GaN films having a thickness of 0.4–0.5 μm have also been grown via the same technique on AlN buffer layers without post-processing annealing.