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This letter reports on AlGaN/GaN high-electron-mobility transistors (HEMTs) on high-resistive silicon substrate with a record maximum oscillation cutoff frequency FMAX. Double-T-shaped gates are associated with an optimized technology to enable high-efficiency 2-D electron gas control while mitigating the parasitic resistances. Good results ogate-length HEMTf FMAX = 206 GHz and FT = 100 GHz are obtained for a 90-nm gate-length HEMT with 0.25-μm source-to-gate spacing. The associated peak extrinsic transconductance value is as high as 440 mS·mm-1. To the authors' knowledge, the obtained FMAX and Gmext are the highest reported values for GaN HEMTs technology on silicon substrate. The accuracy of the cutoff frequency values is checked by small-signal modeling based on extracted S-parameters.