Identification of multivalent molybdenum impurities in SiC crystals

In this paper we summarize parts of our electron spin resonance (ESR) results on Mo(3+)and Mo(4+) centers in SiC polytypes. Further we present the identification of Mo(5+)in 6H-SiC via ESR. Thus Mo is a multivalent impurity in SiC polytypes, acting both as a donor and/or an acceptor. This makes it a possible candidate for residual acceptor and donor compensation. The ESR nuclear hyperfine structure of different Mo isotopes in SiC is resolved for the first time. Mo impurities are shown to occur not only in intentionally doped crystals, but also in commercial 6H- and 4H-SiC wafer material.