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.

I. Introduction

Diamond is a promising semiconductor material for high power, high temperature and high-frequency electronic devices, due to its high breakdown field (33 times as that of Si and 16 times as that of GaAs), highest thermal conductivity (15 times as that of Si and 50 times as that of GaAs) and low dielectric constant (5.7) [1]. However, it is very difficult to synthesize single-crystal diamond films of area greater than 10×10 mm for integrated circuit applications.