Characteristics of Au/Ti/p-diamond ohmic contacts prepared by r.f. sputtering

Low-resistance ohmic contacts were fabricated on diamond films by boron ion implantation and subsequent Ti/Au bilayer metallization. The I-V measurements showed that the as-deposited contacts were ohmic. After annealing at 500 degreesC for 10 min in a vacuum of 10(-4) Pa, the I-V characteristics were improved significantly. As a result of annealing, the specific contact resistance (pc) value, measured by the circular transmission line model (CTLM), decreased from 6.2 x 10(-3) to 1.2 X 10(-6) Omega (.) cm(2). Compared with the value calculated by the transmission line model (TLM), the rho (C) value was reduced by more than two orders of magnitude for the annealed contacts. The CTLM should be more accurate in measurement than the TLM. The changes of the rho (C) value with the operating temperature indicated that the rho (C) value decreased with increasing operating temperature at low temperatures. Tunnelling was suggested to be the dominant transport mechanism at the metal/diamond interface. The band model was quantified. Copyright (C) 2001 John Wiley & Sons, Ltd.