Ultrashallow TiC source/drain contacts in diamond MOSFETs formed by hydrogenation-last approach

Applying the hydrogen (H) radical exposure at the last step of MOSFET fabrication process, an oxygen (O)-terminated channel was converted to a H-terminated one to obtain subsurface hole accumulation for field-effect transistor operation. Low-resistive titanium carbide (TiC) source/drain and alumina gate oxide were resistant to the hydrogenation process. The shallow TiC side contacts (∼3 nm in depth) to the hole accumulation layer (channel) showed good ohmic contacts with a specific contact resistance of 2 × 10^-7-7 × 10^-7 Ω · cm². For diamond MOSFETs with the TiC ohmic layer, the saturated maximum drain current and maximum transconductance reached 160 mA/mm and 45 mS/mm, respectively. An f_T of 6.2 GHz and an f_max of 12.6 GHz were obtained. The hydrogenation-last approach is a nondestructive method for the fabrication of diamond MOSFET with high production yield.