Cutoff frequency increase of gate recessed AlGaN/GaN MISHFETs with amorphous AlN insulator

The RF performance of gate recessed MISHFET devices with an amorphous AlN layer was investigated by small-signal (S-parameter) measurements. They reveal current gain and unilateral power gain cutoff frequencies of 125 and 138 GHz, respectively. These device parameters were achieved for gate recessed MISHFET devices after applying a selective “step by step” etching T-gate formation procedure. The results indicate that the combination of an amorphous AlN dielectric layer with the gate recessed AlGaN/GaN MISHFET structures affects the RF performance in devices prepared for high frequency operation advantageously.