Periodic Reporting for period 2 - ONCHIPS (On-chip integration of quantum electronics and photonics)
Reporting period: 2024-04-01 to 2025-09-30
A major roadblock for silicon-based optoelectronics and its quantum applications is that conventional cubic silicon has an indirect band gap, and hence it is optically inactive. ONCHIPS will capitalize on a recent breakthrough from within its consortium: growth and optical characterization of a revolutionary new material: hexagonal germanium-silicon (hex-GeSi), which is a silicon-based, optically active, direct-bandgap semiconductor. Building on this discovery, ONCHIPS' key objectives are as follows:
(1) We will for the first time grow advanced hex-GeSi heterostructures for quantum technology applications. (2) We will realise spin qubits in quantum dots in hex-GeSi. (3) We will create spin-photon interfaces in hex-GeSi, made possible by the direct bandgap of the material. (4) We will build single-photon detectors for wavelengths beyond 2 micrometers, optimized for emission from hex-GeSi.
This project will foster the integration of electronic and optoelectronic functionalities based on a silicon-based direct-bandgap semiconductor, using a combination of facilities and expertise that is available only in Europe. Hence ONCHIPS will establish a strong contribution to European innovation leadership in electronics, photonics, emerging enabling technologies in general, and quantum technologies in particular, making our contributions highly relevant for the work program. This new material has the potential to be compatible with standard silicon-based semiconductor technology, benefitting from established roadmaps on miniaturization and scalability.
(1) We will for the first time grow advanced hex-GeSi heterostructures for quantum technology applications. (2) We will realise spin qubits in quantum dots in hex-GeSi. (3) We will create spin-photon interfaces in hex-GeSi, made possible by the direct bandgap of the material. (4) We will build single-photon detectors for wavelengths beyond 2 micrometers, optimized for emission from hex-GeSi.
This project will foster the integration of electronic and optoelectronic functionalities based on a silicon-based direct-bandgap semiconductor, using a combination of facilities and expertise that is available only in Europe. Hence ONCHIPS will establish a strong contribution to European innovation leadership in electronics, photonics, emerging enabling technologies in general, and quantum technologies in particular, making our contributions highly relevant for the work program. This new material has the potential to be compatible with standard silicon-based semiconductor technology, benefitting from established roadmaps on miniaturization and scalability.
During reporting period 2, ONCHIPS made significant progress across all work packages. TU Eindhoven and CNRS Saclay achieved controlled growth and passivation of hex-SixGe nanowires, formation of heterostructures and development of Ge rich quantum dots, providing a solid foundation for quantum devices. University of Twente focused on the fabrication and electrical characterization of ~100 SiGe nanowire devices, achieving improved contact quality, lower Schottky barriers, and device operation down to 4 K. Deterministic deposition and structural verification of hexagonal SiGe nanowires were successfully demonstrated, establishing a robust platform for low-temperature transport studies. Advanced single-photon detectors and mid-infrared spectrometers were developed by Single Quantum, while quantum nanostructures were integrated into photonic cavities to enhance emission by TU Munich. University of Konstanz and Budapest University of Technology and Economics (BME) delivered comprehensive theoretical models for hexagonal Ge nanowires and quantum dots, enabling accurate predictions of spin behavior and supporting the design of spin qubits.
ONCHIPS produced several significant scientific outputs during reporting period 2. Key experimental results include the formation of quantum dots and heterostructures in hexagonal SiGe nanowires (CNRS, in preparation) and the demonstration of dimension-controlled single-branched hexagonal SiGe nanowires (TUE, Nano Lett., 2025). Optical properties were further explored through STEM-EELS experiments and ab initio theory, revealing insights into optical absorption in hexagonal Si and Ge nanowires (CNRS, Nano Lett., 2025). Photonic crystal nanocavities for hex-SiGe nanowires were investigated (TU Munich, in preparation). Significant theoretical advances were reported by BME, including studies on g-tensor limitations for semiconductor spin qubits (BME, Phys. Rev. B, 2025), spin-phonon coupling and spin relaxation via lattice reorientation in hexagonal germanium nanowires (BME, 2025). These outputs were actively disseminated through presentations at conferences and deliverable reports, advancing both fundamental understanding and potential applications in quantum devices and spin-based computing. Single Quantum developed and optimized superconducting nanowire single-photon detectors for the 2.3–3.4 μm range, integrating them into a custom detection system that enables unprecedented single-photon sensitivity for characterizing spin dynamics in hex-GeSi nanowires and quantum dots. ONCHIPS consortium partners actively collaborate with industry and end-users and identified five Key Exploitable Results with patent potential among others 2 filed patents, and early-stage evaluations.