A 50-nm Gate-Length Metamorphic HEMT Technology Optimized for Cryogenic Ultra-Low-Noise Operation

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 Ku-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 Ku-band.