High fmax × LG Product of AlGaN/GaN HEMTs on Silicon With Thick Rectangular Gate

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 Ω-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.