Influence of Double-Deck T-gate Structures on Cut-Off Frequency in Al0.7Ga0.3N/AlN/GaN HEMTs

This study investigates the impact of various T-gate structures on the performance of Al0.3Ga0.7N/AlN/GaN HEMTs fabricated on SiC substrates. Five T-gate designs were analyzed, comprising a conventional T-gate and four double-deck T-gate variations. Reducing the width of the source-side 2nd foot resulted in a cut-off frequency (ft) improvement of up to 7 GHz, while the head position was found to have minimal impact. Through capacitance calculations, the contribution of the 2nd foot width to the ft enhancement was analyzed.