OHMIC CONTACTS TO EPITAXIAL AND NATURAL DIAMOND

We have used the circular transmission line test structure of Reeves (Solid State Electron, 23 (1980) 487-490) in order to determine the specific contact resistance of various metals to semiconducting diamond. Sample types included highly doped epitaxial films on [100] and [110] type IIa substrates, type IIb diamonds 0.25 mm thick, and type IIb diamonds thinned to 0.05 mm in thickness, Metallizations tested include the carbide forming refractory metals Ti and Mo, as well as Al, Ni, Au, Pt, and Pd. Measured specific contact resistances ranged from 2 x 10(-5) for contacts to highly doped layers to 1 x 10(-2) OMEGA cm2 for contacts to natural bulk type IIb diamonds. Ohmic contact behavior was not observed for non-carbide forming metallizations on lightly doped type IIb diamond, either in the as-deposited state, or after annealing.