High-frequency performance of diamond field-effect transistor

The microwave performance of a diamond metal-semiconductor field-effect transistor (MESFET) is reported for the first time. MESFETs with a gate length of 2-3 μm and a source-gate spacing of 0.1 μm were fabricated on the hydrogen-terminated surface of an undoped diamond film grown by microwave plasma chemical vapor deposition (CVD) utilizing a self-aligned gate fabrication process. A maximum transconductance of 70 mS/mm was obtained on a 2 μm gate MESFET at V/sub GS/=-1.5 V and V/sub DS/=-5 V,for which a cutoff frequency f_T and a maximum oscillating frequency f_max of 2.2 GHz and 7 GHz were obtained, respectively.