(Invited) High-Speed and Linear Graded-Channel GaN FETs

RF communications with spectral efficiency utilizes complex modulation schemes that require amplifier linearity [1]. As amplifier operating frequency moves into the millimeter wave (mm-wave) range, the power added efficiency becomes also important to save the system prime power. As for 5G applications, high efficiency and linearity of amplifiers are required to support complex waveforms with high peak-to-average ratio (PAPR) and large instantaneous bandwidth. We report the first demonstration of graded-channel GaN HEMTs operating in the millimeter-wave frequency range. At 30 GHz, these graded-channel GaN HEMTs demonstrated excellent PAE of 65% at associated power density of 3 W/mm. The measured PAE and output power density shows great improvement over other mm-wave T-gated AlGaN/GaN HEMT devices. Under two-tone linearity characterization at 30 GHz, PAE of about 50% was demonstrated with C/IM3 of 30 dBc, which is very promising for mmwave linear and efficient amplifiers without digital pre-distortion. This material is based upon work supported by the DARPA under contract number FA8650-18-C-7802. The views expressed are those of the author and do not reflect the official policy or position of the DARPA or the U.S. Government. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the U.S. Government.