Ohmic contacts on (111)-oriented phosphorus-doped diamond fabricated by FIB transformation and surface Ga+ implantation

Abstract

Among the ultra-wide bandgap (UWBG) materials, diamond has unique properties for high power device applications and can deliver p-type and n-type doping. However, the achievement of low resistive ohmic contacts on n-type diamond limits the fabrication of bipolar devices. This study investigates the use of focused Ga+ion beam (FIB) to fabricate metal-free ohmic contacts on phosphorus-doped diamond, with a doping concentration of ∼5 × 1018 cm−3estimated by cathodoluminescence. FIB irradiation was used to locally modify the diamond surface, resulting in a conductive channel with ohmic, albeit highly resistive, behaviour. Using the circular Transfer Length Method (cTLM), a specific contact resistance of 4.3·104 Ω·cm2was obtained. This value is consistent with state-of-the-art results at similar doping levels, demonstrating that FIB is a viable and efficient technique for contact formation in diamond-based electronic devices.