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In this letter, we successfully demonstrated a AlGaN/GaN high-electron mobility transistor on silicon substrate with high product of maximum oscillation frequency (f max ) and gate length (L G ) by reducing the gate resistance (R g ) using a thick, high aspect ratio rectangular gate (R-gate) structure with an L G of 265 nm and thickness of 315 nm which was fabricated using a thick polymethyl methacrylate lift-off process. The maximum drain current is over 1 A/mm, and the peak transconductance is 291 mS/mm. The values of cutoff frequency and f max are 43.7 GHz and 126.5 GHz at a drain voltage (V d ) of 12 V, respectively. R g is extracted through the small-signal model, and the value is given as 0.21 -mm which is comparable to devices with the T-gate structure. This low R g results in a high f max and high f max × L G product of 33.52 GHz-µm, comparable to previously reported GaN-on-Si transistors for both R-gate and T-gate structures.INDEX TERMS AlGaN/GaN, high-electron mobility transistor (HEMT), silicon substrate, power-gain cutoff frequency (f max ), rectangular gate, f max × L G .

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