Growth and doping via gas-source molecular beam epitaxy of SiC and SiC/AlN heterostructures and their microstructural and electrical characterization

Gas-source molecular beam epitaxy has been employed to grown thin films of SiC and AlN on vicinal and on-axis 6H-SiC(0001). Growth using the SiH₄-C₂H4 system resulted in 3C-SiC(111) epilayers under all conditions of reactant gas flow and temperatures. Films of 6H-SiC(OOOl) were deposited on vicinal 6H-SiC(0001) substrates using the SiH₄-C₂H₄-H₂ system at deposition temperatures ≥ 1350°C. In situ doping was achieved by intentional introduction of nitrogen and aluminum into the growing crystal. Monocrystalline AlN was deposited using evaporated Al and ECR plasma derived N or NH3. Films <50Å grown on the vicinal substrates had higher defect densities compared to those on the on-axis substrates due to the higher density of inversion boundaries forming at most SiC steps in the former material. Metal/AlN/6H-SiC (0001) thin film heterostructures which had a density of trapped charges as low as of 1 × 10¹¹ cm^-2 at room temperature were prepared without post growth treatment. Superior single crystal AlN/SiC heterostructures were achieved when very thin AlN was deposited on the on-axis substrates. Single phase monocrystalline solid solutions of (AlN)_x(SiC)_1-x were deposited between 0.2≤×≤0.8. A transition from the zincblende to the wurtzite structure was observed at x≈0.25.