Engineering chlorine-based emitters in silicon carbide for telecom-band quantum technologies

TL;DR

The paper demonstrates chlorine-vacancy (ClV) centers in 4H-SiC as a new class of telecom-band color centers in a CMOS-compatible platform. It reports a controllable fabrication protocol based on Cl implantation and high-temperature annealing, confirms chlorine-specific defect formation through control experiments, and identifies four ClV configurations emitting in the O-, S-, and C-bands with characteristic ZPLs. The optical characterization shows robust ZPL emission up to $30\,rac{K}{K}$ with an activation energy of $E_a = 25\pm11\,\mathrm{meV}$ and outlines optimized implantation fluence ($1\times10^{12}\,rac{cm^{-2}}{cm^{-2}}$) and annealing ($1300^{\circ}\mathrm{C}$) for ensemble creation. These findings position ClV centers as promising telecom-band spin-photon interfaces for scalable quantum networks and motivate future ODMR work and photonic-cavity integration.

Abstract

We report the experimental realization and optical characterization of chlorine-vacancy (ClV) color centers in 4H-SiC emitting in the fiber-optic telecom bands. These defects are created via chlorine ion implantation followed by high-temperature annealing. Photoluminescence spectroscopy reveals four distinct ClV configurations with zero-phonon lines (ZPLs) located in the O-band (1260 - 1360 nm), S-band (1460 - 1530 nm) and C-band (1530 - 1565 nm). Controlled implantation and annealing experiments confirm that the ClV centers originate specifically from chlorine incorporation into SiC and are not intrinsic to this material. We optimize the creation conditions for ClV ensembles and demonstrate negligible reduction of the ZPL intensity up to a temperature of 30 K. These results establish ClV defects as a new class of telecom-band color centers in a CMOS-compatible platform, offering strong potential for scalable quantum networks.

Figures (5)

• Figure 1: Engineering of ClV defects in 4H-SiC. (a) In-depth distribution profile of Cl and Ar ions calculated for the implantation energy $E = 150 \, \mathrm{keV}$. (b) SRIM-simulated probability of creating $\mathrm{V_{Si}}$ per single $\mathrm{Cl^{+}}$ and $\mathrm{Ar^{+}}$ ions. (c) Schematic representation of the $\mathrm{Cl}$ implantation into a HPSI 4H-SiC sample #1 with a thickness of $496 \, \mathrm{\mu m}$. (d) Schematic representation of the $\mathrm{Cl}$ implantation into the 4H-SiC sample #2 with epilayers. (e) Temperature profile of the annealing process. The diagram illustrates the time-dependent temperature evolution, including heating and cooling phases, with annealing conducted at $500 ^{\circ} \mathrm{C}$ (dashed blue), $1100 ^{\circ} \mathrm{C}$ (black) and $1300 ^{\circ} \mathrm{C}$ (dashed red) over 2 hours. (f) Schematic illustration of 4H-SiC coating with a protective carbon cap layer. Arrows indicate the sequence of four key steps used to prevent surface degradation during vacuum annealing: carbon cap deposition, annealing at $1300 ^{\circ} \mathrm{C}$, cap layer removal in oxygen plasma and final surface cleaning.
• Figure 2: Spectral fingerprins of ClV defects in 4H-SiC. (a) Schematic representation of the 4H-SiC lattice with different configuration of chlorine-vacancies in 4H-SiC ClV(hh), ClV(kk), ClV(hk) and ClV(kh). (b) PL spectrum in Cl implanted 4H-SiC wafer with $E = 40 \, \mathrm{keV}$ under $976 \, \mathrm{nm}$ excitation at a temperauture $T = 7 \, \mathrm{K}$. The ZPLs from different configurations of ClV are labeled with arrows. (c) Normalized PL intensity of the ClV1 ZPL at $\lambda =1350 \, \mathrm{nm}$ and background (bkg) at $\lambda =1340 \, \mathrm{nm}$ for different excitation laser wavelength.
• Figure 3: Optical fingerprints of color centers in 4H-SiC. (a) PL spectra in HPSI 4H-SiC at a depth $z = 0 \, \mathrm{\mu m}$ after annealing at $1100 ^{\circ} \mathrm{C}$ over 2 hours without implantation compared to Ar and Cl implantation at an energy $E = 150 \, \mathrm{keV}$ and to a fluence $\Phi = 1 \times 10^{12} \, \mathrm{cm ^{-2}}$. The vertical arrows indicate the ZPLs of divacanccies (PL4 and PL1/PL2), tungsten substituting silicon ($\mathrm{w_{Si}}$), nitrogen-vacancy NV3, vanadium in different lattice cites $\mathrm{V (\alpha)}$ and $\mathrm{V (\beta)}$ as well as of chlorine-vacancy (ClV) and its possible PSB. (b) The same as (a) but measured at a depth $z = 200 \, \mathrm{\mu m}$ below the implanted surface. (c) PL spectra in epetaxial 4H-SiC at a depth $z = 0 \, \mathrm{\mu m}$ after annealing at $1100 ^{\circ} \mathrm{C}$ over 2 hours without implantation compared to Ar and Cl implantation at an energy $E = 150 \, \mathrm{keV}$ and to a fluence $\Phi = 1 \times 10^{12} \, \mathrm{cm ^{-2}}$. The vertical arrows indicate the ZPLs of nitrogen-vacancies NV4, NV3, NV1/NV2 as well as of chlorine-vacancy (ClV) and its possible PSB. (b) The same as (a) but measured at a depth $z = 200 \, \mathrm{\mu m}$ below the implanted surface.
• Figure 4: Dependence on implantation fluence and annealing temperature. (a) PL spectrum at different implantation fluences for an annealing temperature of $1100 ^{\circ} \mathrm{C}$. The arrow indicates the spectral position of the ClV ZPL. The decrease in PL intensity within the shaded spectral region is attributed to reduced reflection of the dichroic mirror. (b) Ratio ClV ZPL to the PL background for different implantation fluences $\Phi$. (c) PL spectra plotted on a logarithmic scale, measured after Cl implantation to a fluence $\Phi = 1 \times 10^{12} \, \mathrm{cm ^{-2}}$ and subsequent annealing at different temperatures.
• Figure 5: PL power and temperature dependence. (a) Intensity of the ClV ZPL and backgroud as a function of the laser power $P$ with the excitation wavelength of $976 \, \mathrm{nm}$. The solid lines are linear fits. (b) 2D color plot showing temperature evolution of the PL spectrum. (c) Temperature dependence of the ZPL from divacancies PL4 and PL1/PL2 together with the ClV. The solid lines are fit to Eq. (\ref{['Activation_Energy']}).