Mechanisms of self-heating in cryogenic high-electron mobility transistors

Cryogenic low-noise amplifiers employ high-electron mobility transistors to amplify the readout signals of quantum computers and quantum sensors. While these components benefit from the cryogenic environment to achieve reduced noise levels, they are limited by self-heating, which causes a minimum noise level that is independent of the ambient temperature below 4-10 K. The characterization of self-heating has remained challenging, as traditional methods have relatively low temperature resolution and require elevated power levels to generate observable temperature increases. Furthermore, the phonon bath inside and around the device cannot readily be assumed to be in equilibrium with the electronic system. In this work, we use Shubnikov-de Haas quantum oscillation thermometry to determine the electron temperature in a high-performance cryogenic amplifier with high temperature resolution. We detect four distinct regimes of energy dissipation, and find links between self-heating, electron-electron interactions, i.e. hydrodynamic transport, as well as acoustic phonon emission. These insights can inform future amplifier designs with improved resilience to self-heating and reduced noise, to support next-generation quantum computers. We determine the self-heating in cryogenic high-electron mobility transistors using Shubnikov-de Haas thermometry. At elevated power levels, electrons cannot be cooled down below about 20 K due to phonon interactions, which explains the inability of low-noise amplifier noise performance to improve below this temperature.