Step dynamics in the homoepitaxial growth of 6H-SiC by chemical vapor deposition on 1° offcut substrate using dichlorosilane as Si precursor

摘要

Step flow epitaxial growth was achieved on 1° offcut 6H-SiC substrate using dichlorosilane (DCS) as the Si precursor. High crystal quality and polytype uniformity were verified by XRD and Raman spectroscopy. Mirror-like surfaces with very few triangular and carrot defects were obtained over a wide range of C/Si ratios. Surface step bunching and step crossover were observed and rms roughness values were measured to be 2–4 nm. N-type doping was achieved by site-competition epitaxy at low C/Si ratios. Growth rates of 0.5-4 μm/h was obtained over a temperature range of 1470–1550 °C. The surface diffusion length of the adatoms on the step terraces was calculated using a model based on the Burton-Cabrera-Frank theory of epigrowth on stepped surfaces. In the experimental temperature range, the surface diffusion length varied from 5 to 13 nm, which is significantly shorter than those reported in literature for epigrowth using the conventional silane precursor. The short diffusion lengths for DCS imply a strong desorption process at the growth front, which is ideal for polytype-matched step-flow growth on low offcut substrates. The understanding of these step dynamics issues is critical for crystal growers using chlorinated gas precursors.