'Anomalous' nitrogen in silicon carbide

An analysis of experimental data on the optical properties of 6H-SiC indicates the existence of deeper donor levels than those for the three crystallographically nonequivalent positions of nitrogen as a substitutional impurity in the carbon sublattice. The complete system of the energy levels of nitrogen in 6H-SiC is examined with allowance for the possibility of the existence of chemically nonequivalent donor positions in addition to the crystallographically nonequivalent positions. This explains the nature of the anomalous IR absorption spectra and 'red' photoluminescence of 6H-SiC:B, N of the n type.