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In this paper, the design, analysis, and room-temperature performance of two W-band LNA MMICs fabricated in two different technology variations are presented. The investigation demonstrates the noise improvement of the given 50-nm gate-length InGaAs mHEMT technology with reduced necessary drain currents. Therefore, a single-ended and balanced W-band LNA MMIC were designed, fabricated, and characterized. The amplifiers exhibit state-of-the-art noise temperatures with an average value for the single-ended LNA of 159 K (1.9 dB) with lowest values of 132 K (1.6 dB). Due to the technology investigation it was possible to reduce the noise temperature by about 15 K compared to the reference technology in combination with superior MMIC yield.

This article reports on the investigation and optimization of cryogenic noise mechanisms in InGaAs metamorphic high-electron-mobility transistors (mHEMTs). HEMT technologies with a gate length of 100, 50, and 35 nm are characterized both under room temperature and cryogenic conditions. Furthermore, two additional technology variations with 50-nm gate length are investigated to decompose different noise mechanisms in HEMTs. Therefore, cryogenic extended K u-band low-noise amplifiers of the investigated technologies are presented to benchmark their noise performance. Technology C with a 50-nm gate length exhibits an average effective noise temperature of 4.2 K between 8 and 18 GHz with a minimum of 3.3 K when the amplifier is cooled to 10 K. The amplifier provides an average gain of 39.4 dB at optimal noise bias. The improved noise performance has been achieved by optimization of the epitaxial structure of the 50-nm technology, which leads to low gate leakage currents and high gain at low drain current bias. To the best of the authors' knowledge, this is the first time that an average noise temperature of 4.2 K has been demonstrated in the K u-band.

This letter presents the design, performance, and analysis of four low-noise amplifier (LNA) monolithic microwave integrated circuits (MMICs) operating in W-band. Two LNA designs were fabricated in two variations of a 20-nm gate-length metal-oxide-semiconductor high-electronmobility transistor (MOSHEMT) technology each. While for the first technology version the heterostructure is directly grown on the final gallium arsenide (GaAs) wafer, the second version uses direct wafer bonding to transfer the III-V heterostructure after the epitaxial growth to a silicon (Si) substrate. Based on the measured noise figure (NF) of the four MMICs over a comprehensive set of bias conditions, the impact of short-channel effects on the RF performance and possible improvements are analyzed. The first LNA covers an octave bandwidth with more than 15 dB of gain and an average NF (75-105 GHz) of 3.5 dB on a Si substrate. At 80 GHz, the second amplifier exhibits minimal NFs of 2.3 and 2.5 dB on GaAs and Si substrates, respectively. Compared to previously reported MOS-or Si-based technologies, the presented LNAs demonstrate state-of-the-art noise performance emphasizing the importance of electron confinement for highly scaled transistor technologies.

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