Cryogenic In0.8Ga0.2As Quantum-Well High-Electron Mobility Transistors from Lowpower Quantum Computing to Tera-Hz Applications

Paper in proceeding, 2025

We present cryogenic In0.8Ga0.2As QW HEMTs with a gate length (Lg) of 35 nm, achieving a record combination of low-power and high-frequency performance. A meticulous modeling of source resistance (Rs) incorporating ballistic channel resistance (Rball) - provides key insights for advancing low-power quantum computing and terahertz (THz) applications. At 4 K, the fabricated device exhibits exceptional performance metrics, including a minimum subthreshold-swing (Smin) of 4.41 mV/dec., a gm-max of 2.49 mS/μ m, and the highest record fT of 813 GHz, with an average gain-bandwidth product (favg) of 810 GHz. These results stem from a tightly controlled gate-recess process, minimizing the side length (Lside) to below 20 nm. Delay-time analysis indicates further THz performance can be achieved by scaled Lg below 20 nm and reducing fringing gate capacitance (Cg-fringe) by 20%. This work demonstrates the potential of cryogenic In0.8Ga0.2As QW HEMTs to revolutionize quantum computing and THz electronics