Metamorphic HEMT technology for low-noise applications

Different noise sources in HEMTs are discussed, and state-of-the-art low-noise amplifiers based on the Fraunhofer IAF 100 nm and 50 nm gate length metamorphic HEMT (mHEMT) process are presented. These mHEMT technology feature an extrinsic f_T of 220 / 375 GHz and an extrinsic transconduction g_{m, max} of 1300 / 1800 mS/mm. By using the 50 nm technology several low-noise amplifier MMICs were realized. A small signal gain of 21 dB and a noise figure of 1.9 dB was measured in the frequency range between 80 and 100 GHz at ambient temperature. To investigate the low temperature behaviour of the 100 nm technology, single 4 * 40 mum mHEMTs were integrated in hybrid 4 - 8 GHz (Chalmers) and 16 - 26 GHz (Yebes) amplifiers. At cryogenic temperatures noise temperatures of 3 K at 5 GHz and 12 K at 22 GHz were achieved.