Cryogenic RF Transistors and Routing Circuits Based on 3D Stackable InGaAs HEMTs with Nb Superconductors for Large-Scale Quantum Signal Processing.

Cryogenic RF transistors and routing circuits operating with extremely low power are essential as control/readout electronics for future large-scale quantum computing (QC) systems. In this work, we demonstrate 3D stackable InGaAs HEMT-based cryogenic RF transistors and routing circuits integrated with Nb superconductors for ultra-low power operation. As a result, we achieve a record high unity current gain cutoff frequency $(f_{T})$ of 601 GHz and unity power gain cutoff frequency $(f_{MAX})$ of 593 GHz at 4 K with the smallest power dissipation among ever reported cryogenic RF transistors. Furthermore, using a novel structure with Nb superconductor and III-V heterostructure hybrid interconnect of the routing circuits, we achieve high-performance routing circuits with 41% lower power dissipation compared to the conventional structure.