Formation of C-centers in Si-based systems by light ion irradiation

TL;DR

This work addresses the challenge of generating telecom-band single-photon emitters in silicon by employing light-ion irradiation to form C-centers—oxygen-carbon interstitial complexes—in Si. The authors combine TRIM simulations, Raman analysis, and temperature- and time-resolved photoluminescence to show that H+ and He+ irradiation produces optically active C-centers with emission near 1560 nm, and they identify dual radiative/nonradiative pathways consistent with singlet and thermally populated triplet states. They also demonstrate C-center formation in Ge-on-Si heterostructures, enabling integration of telecom emitters with efficient photodetection in a common platform. Overall, the results provide a scalable, annealing-friendly route to telecom quantum emitters compatible with silicon photonics and potentially transformative for integrated quantum communication technologies.

Abstract

Atomic-scale crystal defects in Si are quantum-light sources offering tantalizing integration with existing photonic technologies. Yet, the controlled creation of near-infrared color centers for long- haul quantum communication and information still remains a challenge. In this work, we utilize light ions, such as H+ and He+, to gently generate quantum emitters in a crystalline Si matrix. Temperature-dependent photoluminescence measurements demonstrate the presence of optically-active defects, whose fluorescence matches the primary telecom window around 1550 nm. In addition, time-resolved investigations unveil long-lived excitonic states in the μs regime, thus confirming the formation of interstitial oxygen-carbon complexes, termed C-centers. Finally, we explored controlled ion irradiation strategies to seamlessly generate C-centers also in Ge-on-Si heterostructures, which offer an advanced technological platform for the future realization of integrated quantum photonics. This analysis, informed by practical color center synthesis and proof-of-principle experiments in epitaxial architectures, indicates intriguing prospects and profitable strategies to advance the burgeoning field of light-based quantum technologies.

Figures (3)

• Figure 1: Effect of $\mathrm{H^+}$ and $\mathrm{He^+}$ irradiation on silicon with different doping types.a) Calculations based on the Transport of Ions in Matter (TRIM) software of the vacancy distributions generated in Si by $\mathrm{H^+}$ and $\mathrm{He^+}$ with energies of 0.5 and 1 MeV; b) Raman spectra of n-Si (irradiated with $\mathrm{He^+}$ at 0.5 MeV and a dose of 1014 ions/cm2) comparing the irradiated and not-irradiated regions; c) PL spectra at 4 K of a not-irradiated Si sample and an irradiated one with 1 MeV $\mathrm{H^+}$ and a dose of 1014 ions/cm2 for three different doping materials: i-Si, n-Si and p-Si. The middle panel shows the atomic and electronic structures of the C-center.
• Figure 2: Characterization of the C-center generated in irradiated n-Si.a) Ensemble PL spectra showing of the C0- and C1-lines and a new line, NL, likely not belonging to the C-center, generated by 1 MeV $\mathrm{H^+}$ and a dose of 1014 ions/cm2. The spectra are measured from 4 K to 105 K; b) Integrated area of the C0 peak reported in panel a) as a function of the temperature. The solid line is the fit of the experimental data for T > 25 K with an Arrhenius function (Eq. \ref{['eq:T_fit']}). Integrated area of the C1 peaks - generated by 0.5 MeV $\mathrm{He^+}$ irradiation with a dose of 5$\times$1014 ions/cm2 - and Arrhenius fit (solid line) for < 20 K; c) Temperature dependence of $\Delta E=E_{ZPL}(T)-E_{ZPL}(T=0 K)$ and associated fit (solid line) for the C0-line with the model proposed by Ref. passler1997basic; d) Temperature dependence of the full width at half maximum (FWHM) and modeling (solid line) based on Eq. \ref{['eq:G_fit']}; e) Experimental PL lifetime measured at 15 K of the C0-line generated by 1 MeV $\mathrm{H^+}$ and a dose of 1014 ions/cm2 along with the corresponding double-exponential fit (solid line). The inset shows a magnified view of the curve within the first $\sim$25 $\mu$s. f) Temperature dependence of the two decay components ($\tau_1$ and $\tau_2$) in a logarithmic scale.
• Figure 3: Generation of C-centers in Ge-on-Si heterostructures.a) Artistic concept of a Ge-on-Si-based quantum device embedding emitters in Si in the form of C-centers, while the photodetection functionality is provided by Ge. b) Vacancy distributions computed by TRIM for 1 MeV $\mathrm{He^+}$ and $\mathrm{H^+}$ in Ge-on-Si heterostructure; c) Low temperature PL spectra of a non-irradiated Ge-on-Si heterostructure (grey curve) and an irradiated one with $\mathrm{He^+}$ of 1 MeV and a dose of 1015 ions/cm2 (red curve); d) Spectra of the irradiated Ge-on-Si sample with $\mathrm{He^+}$ of 1 MeV and a dose of 1015 ions/cm2 (purple curve) and of the same heterostructure after the removal of the Ge top layer through H2O2 etching (yellow curve).