Schottky-barrier behavior of metals onn- andp-type6H−SiC

The Schottky-barrier height of a number of metals (Ti, Ni, Cu, and Au) on n- and p-type Si-terminated $6H-\mathrm{SiC}$ has been measured in the temperature range 150–500 K. It is found that the barrier height to n-type $6H-\mathrm{SiC}$ does not exhibit a temperature dependence, while for p-type $6H-\mathrm{SiC}$ the change in the barrier height with temperature follows very closely the change in the indirect energy gap in $6H-\mathrm{SiC}.$ These results are inconsistent with models of Schottky-barrier formation based on the concept of a charge neutrality level. Furthermore, the present results cannot be reconciled with a defect pinning mechanism, contrary to the conclusions of earlier studies on III-V compound semiconductors. We suggest that chemical bonding at the metal-semiconductor interface plays an important role in determining the Schottky-barrier height.