EVALUATION OF OHMIC CONTACTS FORMED BY B-AU METALLIZATION ON DIAMOND(IMPLANTATION AND TI)

Low-resistance ohmic contacts have been fabricated on a naturally occu rring B-doped diamond crystal and on polycrystalline diamond films by B ion implantation and subsequent Ti/Au bilayer metallization. A high B concentration was obtained at the surface by ion implantation, a pos t-implant anneal, and a subsequent chemical removal of the graphite la yer. A bilayer metallization of Ti followed by Au, annealed at 850-deg rees-C, yielded specific contact resistance (rho(c)) values of the ord er of 10(-5) OMEGA cm2 for chemical vapor deposition grown polycrystal line films and the natural IIb crystal. The rho(c) values from transmi ssion line model measurements on three different contact configuration s, namely, standard rectangular pads, rectangular pads on diamond mesa s, and three-ring circular structures have been compared. These contac ts were stable to a measurement temperature of approximately 400-degre es-C and no degradation due to temperature cycling was observed. Chemi cal analysis by x-ray photoelectron spectroscopy (XPS) in conjunction with Ar+ sputter depth profiling of the annealed samples indicated tha t the Au overlayer was not effective in preventing oxidation of the un derlying Ti. The XPS study also indicated the formation of TiC at the Ti/diamond interface.