DC and microwave performance of recessed-gate GaN MESFETs using ICP-RIE

Abstract

The fabrication and characterization of GaN MESFETs grown on sapphire recessed using inductively-coupled-plasma reactive ion etching (ICP-RIE) are reported for the first time. The MESFETs were recessed using a Cl 2/Ar plasma in ICP-RIE, and the drain current was monitored during recess. The devices with a gate length of 0.25 μm exhibited a peak extrinsic transconductance of 36 mS/mm and a threshold voltage of −3.7 V. The unity current gain cutoff frequency f T and maximum frequency of oscillation f max were measured to be 28 and 55 GHz, respectively at room temperature. This recessed-gate process produced high extrinsic transconductances and lower threshold voltages compared with those of unrecessed GaN MESFETs. Also, the values of f T and f max are at least twice the highest frequency data ever reported for GaN MESFETs. The influence of substrate temperature on the DC and microwave characteristics is also reported.