Heavily Boron-Doped Source/Drain Layers for Low Contact Resistance and Subthreshold Swing in (001) C–H Diamond MOSFETs

The effect of a heavily boron-doped (p+) source/drain (S/D) layers ([B]: 2–8 × 1020cm-3) are examined compared with conventional Au/diamond S/D contacts without p+on the same hydrogen-terminated (C-H) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs). The following points such as contact resistance (Rc), subthreshold swing (SS), on-resistance (Ron) and threshold voltage (Vth) are comparatively investigated between with/without p+layers. The selective epitaxial growth of p+S/D regions in (001) enhances the contact performance with the C-H diamond channel. It reduces theRcbetween the metal S/D contacts and C-H diamond from 5.8 to 1.4 Ω·mm, which is the lowest reported for (001) diamond MOSFETs. For MOSFETs with a p+layer and source-drain length of 2 μm, the SS is ~560 mV/dec, the on-resistance (Ron) is 0.78 mΩ·cm2, and the threshold voltage (Vth) is 3.4 V. In contrast, without the p+layer, the SS is ~1600 mV/dec, theRonis 1.44 mΩ·cm2, and theVthis 13.7 V. Overall, the p+layer is beneficial for the development of high-performance diamond MOSFETs using the (001) surface.