AlGaN/GaN HEMTs break records at IEDM
R Quay and colleagues from the Fraunhofer Institute of Applied Solid-State Physics, will report AlGaN/GaN-on-SiC HEMTs operating at up to 40 GHz. The devices had a gain in excess of 6 dB and a maximum output power of 0.3 W, equating to a power density of 1.23 W/mm for a gate width of 8 x 30 microns (0.24 mm). The CW power-added-efficiency (PAE) was 10% at a drain bias voltage (Vds) of 26 V, while the peak PAE was 16% at Vds = 15 V.
Meanwhile, Kasahara et al. from NEC will describe the first successful watt-level Ka-band power operation of an AlGaN/GaN HFET on SiC. A device with a gate length of 0.25 microns and a gate width of 0.36 mm had a maximum CW output power of 2.3 W at 30 GHz, together with a PAE of 38% and a linear gain of 8.8 dB at Vds = 30 V. The authors believe that the output power of 2.3 W and the power density of 6.4 W/mm are the highest values reported to date for GaN-based devices at Ka-band.
Linearity is also an important characteristic of AlGaN/GaN HEMTs targeted at applications such as wireless base stations. At IEDM, Nagahara et al. from Fujitsu will report excellent linearity characteristics of AlGaN/GaN HEMTs at Vds = 30 V and class AB operation at 1.9 GHz. The devices, grown on SiC, exhibited a third-order intermodulation distortion (IM3) of –34.7 dBc for an output power level of 26 dBm (backed off 8 dBm from the saturation power). The RF performance is attributed to suppressing current collapse under a high applied voltage, using an optimum n-AlGaN donor layer thickness and SiN passivation.
Yi-Feng Wu and colleagues from Cree Lighting will also report excellent linearity of AlGaN/GaN HEMTs at 4 GHz, including an IM3 of –30 dBc and a PAE of 40% with only –2.6 dB back-off. The results can be compared to –30 dBc IM3 and 45% PAE achieved by InP-based HBTs at 10 GHz.