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arXiv:2108.07090 · Physical Review Applied

Observing Er3+ Sites in Si With an In Situ Single-Photon Detector

Ian R. Berkman, Alexey Lyasota, Gabriele G. de Boo, John G. Bartholomew, Brett C. Johnson, Jeffrey Colin McCallum, Bin-Bin Xu, Shouyi Xie, Rose L. Ahlefeldt, Matthew J. Sellars, Chunming Yin, Sven M. J. Rogge

Published Jan 12, 2023• 24 citations
arXivHTMLPDF

Abstract

We present a flexible method to study the optical properties of an ${\mathrm{Er}}^{3+}$ ensemble in $\mathrm{Si}$ accessed via resonant excitation and in situ single-photon detection. The technique allows an efficient resonant photoluminescence detection of optically active centers with weak oscillator strength in transparent crystals without the need for nanofabrication on the sample. We observe 70 ${\mathrm{Er}}^{3+}$ resonances in $\mathrm{Si}$, of which 62 resonances have not been observed in the literature, with optical lifetimes ranging from 0.5 to 1.5 ms. We observe inhomogeneous broadening of less than 400 MHz and an upper bound on the homogeneous linewidth of 0.75 and 1.4 MHz for two separate resonances. These narrow, stable resonances confirm ${\mathrm{Er}}^{3+}$ in $\mathrm{Si}$ as a promising quantum information candidate. We discuss the use of this technique for rapid characterization of future samples, with the aim of enhancing the prevalence of sites which are favorable for quantum information applications.

DOI
10.1103/physrevapplied.19.014037

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We present a flexible method to study the optical properties of an Er3+{\mathrm{Er}}^{3+}Er3+ ensemble in Si\mathrm{Si}Si accessed via resonant excitation and in situ single-photon detection. The technique allows an efficient resonant photoluminescence detection of optically active centers with weak oscillator strength in transparent crystals without the need for nanofabrication on the sample. We observe 70 Er3+{\mathrm{Er}}^{3+}Er3+ resonances in Si\mathrm{Si}Si, of which 62 resonances have not been observed in the literature, with optical lifetimes ranging from 0.5 to 1.5 ms. We observe inhomogeneous broadening of less than 400 MHz and an upper bound on the homogeneous linewidth of 0.75 and 1.4 MHz for two separate resonances. These narrow, stable resonances confirm Er3+{\mathrm{Er}}^{3+}Er3+ in Si\mathrm{Si}Si as a promising quantum information candidate. We discuss the use of this technique for rapid characterization of future samples, with the aim of enhancing the prevalence of sites which are favorable for quantum information applications.
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Spins in silicon that are accessible via a telecom-compatible optical transition are a versatile platform for quantum information processing that can leverage the well-established silicon nanofabrication industry. Key to these applications are long coherence times on the optical and spin transitions to provide a robust system for interfacing photonic and spin qubits. Here, we report telecom-compatible Er3+ sites with long optical and electron spin coherence times, measured within a nuclear spin-free silicon crystal (<0.01% 29Si) using optical detection. We investigate two sites and find 0.1 GHz optical inhomogeneous linewidths and homogeneous linewidths below 70 kHz for both sites. We measure the electron spin coherence time of both sites using optically detected magnetic resonance and observe Hahn echo decay constants of 0.8 ms and 1.2 ms at around 11 mT. These optical and spin properties of Er3+:Si are an important milestone towards using optically accessible spins in silicon for a broad range of quantum information processing applications.
Rare-earth ions (REIs) have incomplete 4f shells and possess narrow optical intra-4f transitions due to shielding from electrons in the 5s and 5p orbitals, making them good candidates for solid-state optical quantum memory. The emission of Er3+ in the telecom C-band (1530 nm–1565 nm) makes it especially attractive for this application. In order to build practical, scalable devices, the REI needs to be embedded in a non-interacting host material, preferably one that can be integrated with silicon. In this paper, we show that Er3+ can be isovalently incorporated into epitaxial Y2O3 thin films on Si (111). We report on the synthesis of epitaxial, single-crystalline Er:Y2O3 on Si with a narrow inhomogeneous linewidth in the photoluminescence (PL) spectra, 5.1 GHz (<100 mK), and an optical excited state lifetime of 8.1 ms. The choice of Y2O3 was driven by its low nuclear spin and small lattice mismatch with Si. Using PL and electron paramagnetic resonance, we show that Er3+ substitutes for Y in the crystal lattice. The role of interfacial SiOx, diffusion of silicon into the film, and the effect of buffer layers on the inhomogeneous PL linewidth are examined. We also find that the linewidth decreased monotonically with film thickness but surprisingly exhibits no correlation with the film crystalline quality, as measured by the x-ray rocking curve scans, suggesting other factors at play that limit the inhomogeneous broadening in Y2O3 films.
Er-doped Si is a promising candidate for quantum information applications due to its telecom wavelength optical transition and its compatibility with Si nanofabrication technologies. Recent spectroscopic studies based on photoluminescence excitation have shown multiple well-defined lattice sites that Er occupies in Si. Here we report a measurement of the Zeeman and hyperfine tensors of a single 167Er3+^{167}\mathrm{Er}^{3+}167Er3+ ion in Si. All the obtained tensors are highly anisotropic with the largest value principal axes aligning in nearly the same direction, and the trace of the lowest crystal field level g\mathbf{g}g-tensor is $17.78\ifmmode\pm\else\textpm\fi{}0.40$. The results indicate that this specific Er site is likely to be a distorted cubic site that exhibits monoclinic (C1{\mathrm{C}}_{1}C1​) symmetry. Finally, zero first-order-Zeeman fields are identified for this site and could be used to reduce decoherence of hyperfine spin states in future experiments.