Sebastien Kerdiles

Silicon is a leading material platform for photonic quantum technologies. However, a key challenge remains the efficient integration of high-performance single-photon sources in the near infrared. Here we present an all-silicon single-photon source at 1217 nm wavelength, fabricated by nanoscale positioning of a single W center in a circular Bragg grating cavity. The operation wavelength corresponds to the W center’s zero-phonon line that is enhanced by the cavity. Under above-gap continuous-wave excitation, we obtain a saturated photon count rate of 1.29 × 10 ⁶ counts/s with pronounced photon antibunching ( g ⁽²⁾ (0) = 0.06 ± 0.02). Triggered operation under weak pulsed excitation produces single photons with 93 ± 2% purity. At saturation, we reveal purity degradation due to repumping processes, that could be mitigated using selective excitation schemes in the future. These results represent a major step towards on-demand sources of indistinguishable single photons in silicon photonics.

The ability to engineer localized surface plasmon resonances at large scale usually relies on precise nanoscale patterning. Here, we demonstrate that mid-infrared plasmonic responses can instead emerge in unpatterned polysilicon films composed of nanometric (5–50 nm) grains, challenging established design paradigms and eliminating the need for external nanostructuring. Using tailored out-of-equilibrium annealing conditions, we show that hyperdoped polysilicon layers exhibit enhanced light–matter interactions that can be tuned across the mid-infrared range. By combining advanced electron microscopy, infrared spectroscopy and finite-difference time-domain electrodynamic simulations, we demonstrate that these remarkable optical properties originate from naturally formed metal–dielectric interfaces at grain boundaries, which support localized surface plasmon resonances. This work opens up a new field in plasmonics centered on polycrystalline semiconductors, paving the way for cost-effective systems that are fully compatible with microelectronic and photovoltaic technologies, and capable of significantly reshaping light–matter interactions in the infrared range.

We demonstrate single-spin spectroscopy of a fluorescent tumbling defect in silicon called the "G center," behaving as a pseudomolecule randomly reorienting itself in the crystalline matrix. Using high-resolution spin spectroscopy, we reveal a fine magnetic structure resulting from the spin principal axes jumping between discrete orientations in the crystal. Modeling the atomic reorientation of the defect shows that spin tumbling induces variations in the coupling to the microwave magnetic field, enabling position-dependent Rabi frequencies to be detected in coherent spin control experiments. By virtue of its pseudomolecule configuration, the G center in silicon is a unique quantum system to investigate the mutual interaction between optical, spin, and rotation properties in a highly versatile material.

This paper explains the potential of a heat conduction based RTA (Rapid Thermal Anneal) system (Levo) to overcome the main shortcomings of conventional lamp heated tools systems for silicide top contact anneal during SiC MOSFET device fabrication. The advantage of conductive heating is that the radiation-related properties, like transparency of the wafer, does not play a role, and consequently, that the whole rapid thermal anneal becomes independent of wafer type. In this study SiC wafers and Si wafers (both 200mm) were annealed consecutively without any system adjustment. The silicon wafers were used to qualify the process (contamination / within-wafer uniformity and wafer-to-wafer repeatability).

We investigate with Atom Probe Tomography (APT) the distribution of boron in a thin superconducting Silicon-On-Insulator film (33 nm) obtained by high-dose ion implantation (2.5 × 1016 at/cm2) and single-pulse laser melting (160 ns). Only 40% of the target dose was found in the superconducting film, indicating a severe loss of dopants upon fabrication. Besides, the extremely rapid growth of SiB3 precipitates during laser melting impedes the incorporation of active boron in the silicon lattice. Overall, SiB3 precipitates and hyperdoped silicon account for 5.0 × 1015 at/cm2 and 1.0 × 1016 at/cm2 of the retained dose, respectively. This partitioning of boron between the two phases is supported by the “isolated active dopants model,” which allowed to trace back the sheet resistance of the film from APT data. Lastly, the superconducting critical temperature of the present film (0.39 K) is relatively high in view of the computed concentration of active boron (2.3 × 1021 cm−3). This highlights the interplay between doping and strain relaxation in the establishment of superconductivity.

We present superconducting monocrystalline silicon-on-insulator thin 33 nm epilayers. They are obtained by nanosecond laser annealing under ultra-high vacuum on 300 mm wafers heavily pre-implanted with boron (2.5 × 1016 at./cm2, 3 keV). Superconductivity is discussed in relation to the structural, electrical, and material properties, a step toward the integration of ultra-doped superconducting Si at large scale. In particular, we highlight the effect of the nanosecond laser annealing energy and the impact of multiple laser anneals. Increasing the energy leads to a linear increase in the layer thickness and to the increase in the superconducting critical temperature Tc from zero (< 35 mK) to 0.5 K. This value is comparable with superconducting Si layers realized by gas immersion laser doping, where dopants are incorporated without introducing the deep defects associated with implantation. Superconductivity only appears when the annealed depth exceeds the initial amorphous layer induced by the boron implantation. Multiple subsequent anneals result in a more homogeneous doping with reduced amount of structural defects and increased conductivity. The quantitative analysis of Tc concludes on a superconducting–non-superconducting bilayer with an extremely low resistance interface. This highlights the possibility to efficiently couple superconducting Si to Si channels.

Laser annealing was employed to trigger the solid-state reaction of a thin Co film (2.5 nm) with undoped Si. A metastable disilicide layer was obtained after one laser pulse close to the melt threshold. Its diffraction pattern, relaxed lattice parameter, and residual resisitivity are consistent with the formation of the defective CsCl structure. The CoSi2 phase was found after prolonging the thermal treatment with additional pulses or rapid thermal annealing. Because CoSi is skipped in the phase sequence, CoSi2 layers are more uniform in thickness, have an increased superconductivity and a reduced formation temperature. This approach is compatible with the SALICIDE process and can be used to form smooth contacts in superconducting or regular transistors.

This paper demonstrates for the first time a new annealing scheme to form p-type junctions in SiC by high temperature ion implantation followed by laser annealing without the use of a protective carbon capping layer. This novel approach leverages higher substrate temperatures during implant to minimize implant-induced defects during ion implantation, which enables the use of reduced thermal budget laser annealing for dopant activation. Laser annealing enables higher surface temperatures in the implanted layer than conventional annealing using a high temperature furnace. The shorter thermal budget results in higher dopant activation while minimizing, the formation of extended defects observed during high thermal budget furnace annealing, which can lead to undesirable degradation in device performance. By using laser annealing with no carbon capping layer, the sheet resistance of the implanted layers is reduced up to 6 times with respect to the conventional process (using a furnace anneal and carbon capping layers).