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We report deep-submicrometer gate-recessed and field-plated AlGaN-GaN HEMTs and their state-of-the-art continuous wave (CW) power performance measured at 30 GHz. The AlGaN-GaN HEMTs exhibit a CW power density of 5.7 W/mm with a power-added efficiency (PAE) of 45% and drain-efficiency of 58% at ds = 20 V. At ds = 28 V, the output power density is measured as high as 6.9 W/mm with both PAE and output power increasing with input power level. Compared to conventional T-gated AlGaN-GaN HEMTs, the output power density and PAE of gate-recessed AlGaN-GaN HFETs are improved greatly, along with the excellent pulsed IVs. We attribute the improvement to both a field-plating effect and a vertical separation of the gate plane from surface states.Index Terms-Field-effect transistor (FET), GaN, HEMT, millimeter-wave (mmWave).

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The authors report on highly scaled 60 nm gate length graded-channel AlGaN/GaN high electron mobility transistors (HEMTs) with a record power added efficiency (PAE) of 75% at 2.1 W/mm power density at Vdd = 10 V and the PAE of 65% at 3.0 W/mm power density at 30 GHz at Vdd = 14 V. Under two-tone power measurement, the graded-channel AlGaN/GaN HEMTs demonstrated similar power performance with peak PAE >70% at 30 GHz. This novel channel design shows great promise for high-efficiency millimetre-wave (mmW) power amplifiers up to 3 W/mm RF power density operation.

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