Ohmic graphite-metal contacts on oxygen-terminated lightly boron-doped CVD monocrystalline diamond

Abstract

A process to obtain ohmic contacts on oxygen-terminated lightly boron-doped CVD monocrystalline diamond films was developed. Samples were contacted by Ti/Au metallic pads in the transmission line model (TLM) configuration. The electric contacts were placed onto a mesa structure produced on the CVD boron-doped layer. One of the samples was additionally implanted with helium ions at 10 keV in order to induce the formation of a graphitic layer underneath the diamond surface before contacting so as to improve electrical conduction. The electrical performance of both devices was characterized by the TLM method and compared. As a result, the sample with metallic electrodes exhibited a small and non-linear electrical conduction, while the graphitic/metallic contacts showed an ohmic behaviour with an estimated specific contact resistance as low as 3.3 × 10−4 Ω·cm2 for a doping level of a few 1017 cm−3. This approach opens the way to more efficient ohmic contacts on intrinsic or low-doped diamond that are crucial for the development of electronic devices and detectors.