Microwave Performance of Diamond Field-Effect Transistors

Abstract

The microwave performance of diamond metal semiconductor field-effect transistors (MESFET) and metal insulator semiconductor field-effect transistors (MISFET) fabricated on hydrogen-terminated diamond surface is investigated. A cut-off frequency of 2.2 GHz is obtained on a 2 µm Cu gate MESFET with a transconductance of 70 mS/mm. A cut-off frequency of 11 GHz is obtained on a 0.7 µm gate MISFET with a transconductance of 40 mS/mm. Despite the lower transconductance, the cut-off frequency of MISFET is higher than that of MESFET due to not only gate minimization but also increased carrier mobility due to the use of CaF2 as the gate insulator. High-frequency equivalent circuits are derived from S-parameters for MISFET with various gate lengths. Reduction of gate-source parasitic resistance and capacitance in MISFET by the improvement of device structure yield high frequency performance.