A High Frequency Hydrogen-Terminated Diamond MISFET With ${f}_{{\text{T}}}/{f}_{\max}$ of 70/80 GHz

A high frequency hydrogen-terminated diamond metal-insulator-semiconductor field-effect transistor (MISFET) with extremely small source-drain distance of about 350 nm was realized by self-aligned process on (001)-oriented single crystal diamond substrate. To suppress the gate leakage current, a low temperature Al
₂
O
₃
film was deposited as the gate insulator by inductance coupled plasma enhanced atomic layer deposition. A low ohmic contact resistance of 1.84 Q·mm was measured by using transmission line method. The fabricated 100 nm gate length MISFET shows a high current density of 585 mA/mm and a high transconductance of 206 mS/mm. By minimizing the parasitic parameters of the device, a high current gain cut-off frequency f
_T
of 70 GHz and maximum frequency of oscillation f
_max
of 80 GHz have been realized.