Identification of molybdenum in 6H-SiC by magnetic resonance techniques

We report on the identification of molybdenum trace impurities in commercial 6H-SiC substrates by conventional and optically detected electron spin resonance (ESR, ODESR) and magnetic circular dichroism (MCD) absorption techniques. The two impurity charge states Mo(exp4+) (4d(exp 2)) and Mo(exp 3+) (4d( exp 3) are identified. Consequently, this impurity is electrically active as a deep level acceptor state. In addition we observe the 3.A2 -> 3.T2 crystal field absorptions of Mo(exp 4+) (4d(exp 2)) in the spectral range 1.1-1.25 eV. The consequences of the present findings, for the use of Mo as an electrical contact material, are pointed out.