Millimeter-wave HEMT technology

The authors report the development of short gate-length (0.15-0.25- mu m) HEMTs (high-electron-mobility transistors) with state-of-the-art noise and power performance. The three families of HEMTs-conventional GaAs/AlGaAs, pseudomorphic, and InP-based-are described and compared. The InP HEMTs offer the lowest noise figure: device noise figures of 0.3 dB at 18 GHz and 1.4 dB at 94 GHz have been measured, and multistage amplifiers with 1.7-dB noise figure at 62 GHz and 3.3 dB at 92 GHz are reported. Pseudomorphic HEMTs that exhibit the best power performance of any millimeter-wave transistor have been developed, with record output powers of 658, 125, and 57 mW at 35, 60, and 94 GHz, respectively, and power-added efficiency as high as 41% at 60 GHz. A 44-GHz pseudomorphic HEMT power amplifier has generated 0.25-W output power with 27% power-added efficiency and 14-dB power gain. Finally, the reliability of the various HEMT types is discussed.<
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