Solubility of nitrogen and phosphorus in 4H-SiC: A theoretical study

The n-type dopants phosphorus and nitrogen, and their complexes with intrinsic point defects are investigated in 4H-SiC by first-principles theory. The solubility and electrical activation of the dopants in thermodynamic equilibrium are calculated. For nitrogen, a saturation of the electrical activation above a certain critical concentration is found that is driven by a preferential incorporation of nitrogen into electrically passive nitrogen-vacancy complexes. This explains the observations of recent experiments. An almost complete phosphorus activation is found up to the solubility limit. We suggest that the low phosphorus doping achieved by sublimation growth is related to the growth kinetics.