Investigation of <1,1,-2,0> Epitaxial Layers Grown on a-Cut 4H-SiC Substrates

We report an experimental investigation of the growth and characterization of low-doped 4H-SiC epitaxial layers deposited on a-cut 4H-SiC substrates. The growth was carried out using standard procedures for optimized {0,0,0,1} 4H-SiC surfaces. The resulting sample thickness was 6-10 mum and, excepting few pyramidal defects, the surface was mirror-like with AFM surface roughness similar to 0.6 nm. Optical investigations have been done using, both, micro-Raman scattering and low temperature photoluminescence spectroscopy. They show a low level of residual doping with only nitrogen and aluminum acting as impurity. Electrical investigations confirm these results.