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 Mo⁴⁺ (4d²) and Mo³⁺(4d³) are identified. Consequently, this impurity is electrically active as a deep level acceptor state. In addition we observe the ³{A}₂→³{T}₂$ crystal field absorptions of ${Mo}⁴⁺$ (4${d}²$) 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. {} 1996 The American Physical Society.