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 Cl2/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 fT and maximum frequency of oscillation fmax 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 fT and fmax 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.
- Gate recess
- Inductively-coupled-plasma reactive ion etching
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering
- Materials Chemistry