Fig. 1: Concept of heterogeneous and monolithic 3D integration of III–V-based electronics on Si towards large-scale quantum computing solutions.

a Present-day quantum computing systems are characterized by a qubit chip operating below 1 K, accompanied by classical microwave electronics functioning at 300 K. These classical microwave electronics, pivotal for control and readout functions, are connected to the qubits via lengthy coaxial cables. Placing control/readout electronics nearer to the qubit chip helps minimize the number of coaxial cables originating from room temperature. The ultimate solution for future large-scale quantum computing systems involves the integration of qubits and cryogenic control/readout electronics onto a single die. Given the constraints in cooling power, the imperative for extremely low-power cryogenic electronics, encompassing routing circuits and amplifiers, becomes evident. b Conceptual image of III-V/CMOS heterogeneous 3D integrated circuits to co-integrate qubits and control/readout electronics on the same chip. Although this work explored 3D integration in Si instead of CMOS, we anticipate that future studies will enable additional functionalities, including integration with foundry-available CMOS-based qubits and digital blocks. c 3D schematic of the proposed cryogenic devices for amplifier and switch, utilizing III-V-based high-mobility two-dimensional gas (2DEG) channels and Nb-based superconductors integrated on Si. The devices for RF signal amplifiers consist of III–V high-electron mobility transistors combined with Nb superconducting material to achieve high-frequency, low-noise, and low-power operation. d Cross-sectional STEM image of III–V heterostructure with T-shaped gate, demonstrating a gate length of 70 nm. Scale bar, 100 nm. e Cross-sectional STEM image of III–V heterostructure with Nb on Si with Al₂O₃ (bonding dielectric), SiO₂ (interlayer dielectric). The InAlAs/InGaAs heterojunction with Si delta doping induces a two-dimensional electron gas (2DEG) in the quantum well (QW) InGaAs layer, providing remarkably high electron mobility at cryogenic temperature. Scale bar, 20 nm. f Cross-sectional STEM image of Nb global interconnect on Si with Al₂O₃ (bonding dielectric), SiO₂ (interlayer dielectric). Scale bar, 20 nm.