Gate-Recessed AlGaN/GaN Based Enhancement-Mode High Electron Mobility Transistors for High Frequency Operation

By combining a low damage chlorine based gate-recess etching and a sophisticated technology for AlGaN/GaN depletion-mode high electron mobility transistors (HEMTs) we fabricated high performance recessed enhancement-mode HEMTs. A comparative investigation of depletion- and enhancement-mode devices prepared by this technique shows excellent DC and RF properties. A transconductance of 540 mS/mm and cut-off frequencies f T of 39 GHz and f max of 74 GHz were obtained for 0.25 µm gate enhancement-mode HEMTs. Large-signal power measurements at 2 GHz reveal an output power density of 4.6 W/mm at 68% PAE conclusively demonstrating the capability of our enhancement-mode devices.