Effect of an intermediate graphite layer on the electronic properties of metal/SiC contacts

Photoelectron spectroscopy and electrical measurements were used to study the graphite/SiC-interface with emphasis on the Schottky barrier formation. The investigations revealed a strong dependence of the Schottky barrier on the surface polarity of SiC. In the case that the graphite layer was prepared on the Si(0001)-face on n-/p-type 4H- and n-/p-type 6H-SiC, the Fermi level is pinned close to the conduction band edge at the interface. The Schottky barrier fabricated on n-type 4H-SiC(0001) is 0.6 eV, whereas on n-type 6H-SiC(0001) it is lower and amounts (0.3-0.55) eV. On p-type 4H-/6H-SiC, the Schottky barrier is prepared on the C-face (000 (1) over bar) of n-type 6H-SiC, the Fermi level is pinned close to the middle of the band gap. In this case, the Schottky barrier height is found to be equal to 1.4 eV. It is demonstrated that the carbon/graphite formation at the interface between metal and n-type 4H-SiC does not ensure ohmic behaviour. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.