11.9 W Output Power at 4 GHz from 1 mm AlGaN/GaN HEMT

A high electrical breakdown field combined with a high electron saturation velocity make GaN very attractive for high power high frequency electronics. The maximum drain current densities of AlGaN/GaN HFETs range from 1.0 A/mm to 1.5 A/mm [1-3]. Hence, it is obvious that breakdown voltages over 160 V are required to achieve record output power densities larger than 30 W/mm [3] for class A operation. Maximum RF output power of GaN based HEMTs is significantly less than what can be estimated from its DC characteristics, the so-called DC to RF dispersion [4]. This gate lag effect and a good passivation of the AlGaN surface under the gate contact are key elements in achieving high power HEMTs.