Periodic Reporting for period 1 - ONCHIPS (On-chip integration of quantum electronics and photonics)
Reporting period: 2022-10-01 to 2024-03-31
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.
ONCHIPS’ dynamic team had a productive first phase of the project. Our partners from CNRS – Saclay and TU Eindhoven thoroughly investigated the growth of SiGe hexagonal nanobranches on GaAs nanowires with various compositions. The first observations towards the fabrication of Ge/GeSi and Si/Ge heterostructures are promising. A proof of concept of a new approach enabling the growth of hexagonal Ge-4H nanowires has been developed by our partner at CNRS considering to patent this process. The wires are expected to emit light near the calculated band gap energies with high potential for telecom applications. The researchers at the University of Twente fabricated several generations of nanowire devices and measured for the first time their electrical transport properties. We made progress towards defining tuneable quantum dots, an important prerequisite for obtaining a spin qubit. The optical spectroscopy measurements on single hex-SiGe nanowires performed by our partner from TU Munich largely confirmed the theoretical predictions. The first luminescence measurements have been performed on two generations of hex-GeySi(1-y)-GexSi(1-x) multiple quantum well samples provided by TU Eindhoven. Single Quantum made excellent progress towards the development of a single-photon detection system based on superconducting nanowires single photon detectors that is tailored to cover the direct bandgap emission of hex-GexSi1-x (2.3-3.4 µm). The system was shipped from Single Quantum and installed in the laboratories of TU Munich to provide a unique detection capability for the measurement of conduction and valence band g-factors in bulk hex GeSi and the measurement of electron and hole g-tensors in hex GeSi quantum wells. Research performed so far by our partners from University of Konstanz and TU Budapest has yielded a theoretical description of hex-GeSi that can be applied to nanostructures based on hexagonal GeSi (hex-GeSi). The developed theory will be used to model spin-dependent transport and optical properties and quantum coherence of the spin degree of freedom. To support the realisation of spin qubits and spin-photon interfaces in hex-GeSi our theory will be used in the next phase of the project to interpret experimental results and provide quantitative guidelines for optimized device design.
The efforts and successes in this first phase of the ONCHIPS project materialized in the form of three manuscripts. In a recent article published in the Journal of Applied Physics, authors from TU Eindhoven report on polarization properties of hex-SiGe nanowires from photoluminescence spectroscopy experiments. The simulations investigating the influence of the dielectric contrast of nanowire structures confirm the polarization selection rules of the lowest optical band-to-band transition in hex-SiGe. The understanding of the selection rules is important for creating light detection devices from hex-SiGe and for developing silicon-based light sources for the realization of active silicon photonics. Two theoretical manuscripts from our partners at University of Konstanz and TU Budapest have been published in the Physical Review B journal. The authors derived a 10-band k·p theory for hexagonal germanium which will be extended to SiGe, obtained the g-factors for hexagonal germanium in various conduction and valence bands, analyzed the Zeeman interaction in double quantum dots in a hex-SiGe wire. Special magnetic field directions with pseudospin conservation have been identified and the phonon dispersion relations and the corresponding phonon modes in hexagonal germanium nanowires have been computed. These results represent an important step toward the precise interpretation and efficient design of spin-based quantum computing experiments in materials with strong spin-orbit coupling.
ONCHIPS consortium partners collaborate with industry and end-users and identified key results with patent potential including the development of growth processes of SiGe nanowires (CNRS-Saclay and TU Eindhoven) and the development of single photon emitters (TU Munich and TU Eindhoven). The long wavelength (2–4 μm) superconducting nanowires single photon detectors developed by Single Quantum have two main potential markets: biomedical imaging and quantum communication. A potential business model is considered, the partners, interacting companies and adopters have been identified and a preliminary market evaluation and a stakeholder analysis have been performed.
ONCHIPS consortium partners collaborate with industry and end-users and identified key results with patent potential including the development of growth processes of SiGe nanowires (CNRS-Saclay and TU Eindhoven) and the development of single photon emitters (TU Munich and TU Eindhoven). The long wavelength (2–4 μm) superconducting nanowires single photon detectors developed by Single Quantum have two main potential markets: biomedical imaging and quantum communication. A potential business model is considered, the partners, interacting companies and adopters have been identified and a preliminary market evaluation and a stakeholder analysis have been performed.