Fabrication of T-Shaped Gate Diamond Metal–Insulator–Semiconductor Field-Effect Transistors

Abstract

Diamond metal–insulator–semiconductor field effect transistors (MISFETs) with gates of 0.2–0.9 µm length and T-shape were realized by trilayer resist electron-beam lithography. FETs show a cut-off frequency ( fT) of 11 GHz and maximum oscillation frequency ( fmax) of 22 GHz. The fmax/ fT ratio of this FET was more than double that of FETs with a conventional gate structure and the same gate length. The fT of 11 GHz was half the maximum for diamond FETs due to parasitic capacitance at the gate–drain and gate–source electrodes. The T-shaped gate structure and the source-to-drain spacing must be optimized to reduce parasitic capacitance between each electrode.