The processing of weak electromagnetic signals at radio frequencies demands for extremely low noise amplifiers (LNAs). InGaAs high-electron-mobility transistors (HEMTs) provide state-of-the-art noise performance. Still, they need to be cryogenically cooled to fulfill the noise requirements of applications such as radio-astronomy or quantum bit read-out. Future cryogenic systems will need to increase the number of LNAs to enhance their performance, which demands for a reduction of the LNA size, power consumption, and noise.This work describes the characterization, modeling, and optimization of HEMTs for cryogenic ultra-low noise amplification. A novel scalable and temperature dependent HEMT model is proposed, which allows for circuit and technology optimizations. Several HEMT technologies are investigated and an optimized version for cryogenic ultra-low-noise amplification is provided. Combining the accurate model data with the optimized technology allows to design LNAs optimized for cryogenic use. As a result, a monolithic 4 – 8 GHz LNA with low footprint, low power consumption, and a noise temperature of 3.6 K is demonstrated, which sets the state of the art among monolithic LNAs.weiterlesen