Identification of optically and electrically active molybdenum trace imputities in 6H-SiC substrates

In this work the identification of molybdenum trace impurities in commercial 6H-SiC substrates by conventional and optically detected electron spin resonance (ESR, ODESR), magnetic circular dichroism (MCD and Fourier transform infrared absorption techniques is reported. The two impurity charge states, Mo(exp 4+)(4d(exp 2)) and Mo(exp 3+)(4d(exp3)), are identified. Consequently, this impurity is electrically active as a deep level acceptor state. In addition we observe the (exp 3)A(ind2) to (exp 3)T(ind 2) crystal field absorptions of Mo(exp 4+)(ed(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.