SiC Dopant Incorporation Control Using Site-Competition CVD

The use of site-competition epitaxy, which is based on intentional variation of the Si/C ratio during epitaxy, has now been reproduced in numerous national and international laboratories. Presented in this paper is a summary of the site-competition technique as a comparison of controlled doping on C-face 6H-SiC(0001-) versus Si-face 6H-SiC(0001) substrates for phosphorous (P), aluminum (Al), boron (B), and nitrogen (N). Also reported herein is the detection of hydrogen in boron-doped CVD SiC epilayers and hydrogen-passivation of the boron-acceptors. Results from low temperature photoluminescence (LTPL) spectroscopy indicate that the hydrogen content increased as the C–V measured net hole concentration increased. Secondary ion mass spectrometry (SIMS) analysis revealed that the boron and the hydrogen incorporation both increased as the Si/C ratio was sequentially decreased within the CVD reactor during epilayer growth. Boron-doped epilayers that were annealed at 1700 °C in argon no longer exhibited hydrogen-related LTPL lines, and subsequent SIMS analysis confirmed the outdiffusion of hydrogen from the boron-doped SiC epilayers. The C–V measured net hole concentration for the B-doped epitaxial layers increased more than threefold as a result of the 1700 °C anneal, which is consistent with hydrogen passivation of the boron-acceptors. For N-doped epitaxy, N incorporation into C-sites is favored on the Si-face whereas N incorporation into the Si-site is apparently the preferred lattice site on the C-face. Both P and N exhibit preferred incorporation on the C-face while Al and B incorporation is more efficient on the Si-face.