4H-SiC homoepitaxy on nearly on-axis substrates using TFS-towards high quality epitaxial growth

We report high quality homoepitaxial growth on nearly on-axis (+/- 0.5 degrees) 4H-SiC substrates by chemical vapor deposition (CVD) using Tetrafluorosilane and Propane as Si and C-precursors, respectively. N-type unintentional doping (10(17)-10(14) cm(-3)) was obtained for 0.6 < C/Si < 2.5, displaying site-competition behavior. Epilayers showing varying degrees of step flow/spiral growth were obtained at growth rates R-g-5-14 mu m/h, which was found to be C-controlled. At C/Si < 2, R-g was weakly dependent on the ratio, with a clear transition from step-controlled growth (0.6 < C/Si < 1) to spiral growth as C/Si increases, as observed by others previously. For C/Si > 2.0, a linear dependence on C-flow is established, with a return to step-mediated growth, shown by the surface morphology (RMS roughness similar to 1 nm), and high polytype uniformity from Raman at high R-g- 14 mu m/h. These two behaviors were ascribed to a decrease in the etch rate of SiC by SiF4 with increasing C/Si due to C-aided decomposition of SiF4, both of which make available a greater amount of elemental Si at the surface, thereby suppressing spiral growth. Use of on axis or near on-axis substrates can eliminate/reduce basal plane dislocations which limit the performance of SiC bipolar electronic devices. (C) 2016 Elsevier B.V. All rights reserved.