Channel mobility evaluation for diamond MOSFETs using gate-to-channel capacitance measurement

In this work, the channel mobility (μ_ch) of diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with hole accumulation layer channels was evaluated from the gate-to-channel capacitance and drain conductance for the first time. The FET structure was utilized for the capacitance-voltage (C-V) measurement, and the gate-to-channel capacitance (C_GC) under the forward bias condition was proportional to the gate area, as in the case of Si MOSFETs. For the accurate evaluation of the drain conductance, diamond MOSFETs were fabricated on IIa-type diamond films with low boron concentrations (< 10¹⁴cm^{- 3}). In a 60-μm gate-length diamond MOSFET, a μ_ch of 145cm²/Vs was obtained, which is comparable to that of a SiC inversion layer.