High-frequency performance of diamond field-effect transistor

The microwave performance of a diamond metal-semiconductor held-effect tran sistor (MESFET) is reported for the first time. MESFETs with a gate length of 2-3 mum and a source-gate spacing of 0.1 mum were fabricated on the hydr ogen-terminated surface of an undoped diamond film grown by microwave plasm a chemical vapor deposition (CVD) utilizing a self-aligned gate fabrication process, A maximum transconductance of 70 mS/mm was obtained on a 2 mum ga te MESFET at V-GS = -1.5 V and V-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 obta ined, respectively.