Hybrid optical–electrical detection of donor electron spins with bound excitons in ​silicon

Journal name:
Nature Materials
Volume:
14,
Pages:
490–494
Year published:
DOI:
doi:10.1038/nmat4250
Received
Accepted
Published online

Electrical detection of spins is an essential tool for understanding the dynamics of spins, with applications ranging from optoelectronics1, 2 and spintronics3, to quantum information processing4, 5, 6, 7, 8. For electron spins bound to donors in ​silicon, bulk electrically detected magnetic resonance has relied on coupling to spin readout partners such as paramagnetic defects4, 5 or conduction electrons6, 7, 8, which fundamentally limits spin coherence times. Here we demonstrate electrical detection of donor electron spin resonance in an ensemble by transport through a ​silicon device, using optically driven donor-bound exciton transitions9, 10. We measure electron spin Rabi oscillations, and obtain long electron spin coherence times, limited only by the donor concentration11. We also experimentally address critical issues such as non-resonant excitation, strain, and electric fields, laying the foundations for realizing a single-spin readout method with relaxed magnetic field and temperature requirements compared with spin-dependent tunnelling12, 13, enabling donor-based technologies such as quantum sensing.

At a glance

Figures

  1. Electrically detected D0X spectroscopy in a silicon device.
    Figure 1: Electrically detected D0X spectroscopy in a ​silicon device.

    a, Schematic of the 31P-doped28Si epitaxial layer (with in-plane strain ε||) on an undoped natural ​Si substrate. b, Energy shifts of the conduction band valleys (X, Y and Z), donor (Ed), and light hole (LH) and heavy hole (HH) valence bands due to ε|| and magnetic field B. c, Allowed transitions for D0X formation at B = 0.35 T (labelled according to convention; ref. 9) and the measured spectrum. d, B dependence of the spectrum, with dashed lines showing fits based on the extracted g-factors and ε||. The green arrow indicates the optical transition used in subsequent measurements. e, Electric field dependence of D0X spectrum at B = 0 T shows the Stark shifts of the LH and HH bands. Dashed lines are linear fits to the LH and HH peak positions.

  2. Electrically detected spin resonance using D0X.
    Figure 2: Electrically detected spin resonance using D0X.

    a, The initial laser pulse hyperpolarizes the electron spins into the | 〉 state, and is followed by a microwave pulse of duration tμw corresponding to some rotation θ (θ = 0, purple trace, or θ = π, red trace). The current transient during the ‘readout’ laser pulse is used to measure the electron spin population in the | 〉 state. b, Magnetic field sweep with a fixed tμw = 100 ns microwave pulse, where the 31P ESR transition with mI = −1/2 is detected. ce, Coherent control and electrical detection of the donor state demonstrated by Rabi oscillations (the microwave power attenuations are as indicated and the traces are offset for clarity) (c), Hahn echo signal for τ = 20 μs (d), and T2 measurement (e). Dashed lines are fits to the experimental data.

  3. ESR detection under D0X laser excitation.
    Figure 3: ESR detection under D0X laser excitation.

    a, Electron spin echo-detected field sweep of the mI = −1/2 hyperfine line of 31P donors in a ​28Si crystal, measured at 4.3 K in thermal equilibrium (blue), and with the laser tuned to transitions 5–6 (red), showing a signal enhancement by a factor of ∼18. b, The dynamics of the hyperpolarization process is studied with the D0X laser tuned to transitions 5–6 (red), tuned off resonance by 3 μeV (purple), and measured with the laser turned off completely (blue). The lack of response when the laser is off resonance indicates non-resonant ionization processes are negligible here.

  4. Strain-induced shifts in D0X transition energies, ΔE[D0X].
    Figure 4: Strain-induced shifts in D0X transition energies, ΔE[D0X].

    a, Uniaxial stress applied along the major crystallographic directions: 〈100〉, 〈110〉 and 〈111〉. The lines are results from our calculation, and circles are data taken from ref. 30. b, Calculated ΔE[D0X] due to thermal expansion coefficient mismatch for 31P donors in close proximity to ​aluminium electrodes and under a 5 nm gate oxide at 4.2 K. Only the higher energy of the two strain-induced valence band branches for the transitions are shown. See Supplementary Information for details.

References

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Author information

Affiliations

  1. London Centre for Nanotechnology, University College London, London WC1H 0AH, UK

    • C. C. Lo,
    • M. Urdampilleta,
    • P. Ross,
    • J. Mansir &
    • J. J. L. Morton
  2. Department of Electronic and Electrical Engineering, University College London, London WC1E 7JE, UK

    • C. C. Lo &
    • J. J. L. Morton
  3. Hitachi Cambridge Laboratory, J. J. Thomson Avenue Cambridge CB3 0HE, UK

    • M. F. Gonzalez-Zalba
  4. Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA

    • S. A. Lyon
  5. Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada

    • M. L. W. Thewalt

Contributions

C.C.L., M.U., M.F.G-Z. and J.J.L.M. conceived and designed the experiments. M.L.W.T. and S.A.L. provided the ​silicon samples. M.U. fabricated the ​silicon device, and the experiments were carried out by C.C.L., M.U. and P.R. C.C.L. developed the strain model for D0X and J.M. performed the strain simulations. All authors discussed the results. C.C.L. and J.J.L.M. wrote the manuscript with input from all authors.

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