Growth and characterization of 4H-SiC epilayers on substrates with different off-cut angles

Abstract

In this paper, epitaxial growth on 4H-SiC (0001) substrates with 4° and 8° off-cut angles is investigated. Both growth rate and nitrogen doping show a dependence on the C∕Si ratio and off-cut angle. Good surface morphologies are obtained on the 8° off-angle substrates over a wide range of C∕Si ratios, while macrostep bunching is observed on the 4° off-angle substrates depending on C∕Si ratios. Step bunching behaviors on both substrate orientations are investigated by Nomarski microscopy and atomic force microscopy, and possible step bunching mechanisms are proposed to explain the results. Basal plane dislocation (BPD) densities are examined by means of molten KOH etching. Low off-cut angle is found to enhance the conversion of BPDs into threading edge dislocations. A BPD density of 2.6cm−2 is achieved on the 4° off-angle substrate under optimized growth conditions. The effects of changing the C∕Si ratio on BPD densities are also investigated.