Catalytic graphitization and Ohmic contact formation on 4H-SiC

Electrical contact properties and graphitic structures of metal/carbon/4H-SiC structures are investigated. Metals studied include Ni, Co, Cr, NiCr, Ti, W, Mo, Al, and Au. Ohmic contacts are formed on Ni/C, Co/C, Cr/C, and NiCr/C films on 4H-SiC with n-type, C-face, and a doping concentration of 1.8x10(19) cm(-3) . Only Ni/C and Co/C films exhibit Ohmic contact behavior on SiC with n-type, Si-face, and a doping concentration of 1.6x10(18) cm(-3). Ni and Co are well known as excellent graphitization catalysts. Raman spectra show that the formation of graphitic carbon is related to the formation of Ohmic contacts in the annealed metal/carbon/SiC structures. Generally accepted catalytic graphitization mechanisms are applied to explain the scanning electron microscopy images, which demonstrate a relationship between the catalytically reacted morphology and Ohmic contact behavior. This study provides evidence that the metals with better catalytic graphitization activities form better Ohmic contacts on metal/carbon/SiC structures. (C) 2003 American Institute of Physics.