Room-temperature single-photon emitters in silicon nitride

Abstract

Single-photon emitters are essential in enabling several emerging applications in quantum information technology, quantum sensing, and quantum communication. Scalable photonic platforms capable of hosting intrinsic or embedded sources of single-photon emission are of particular interest for the realization of integrated quantum photonic circuits. Here, we report on the observation of room-temperature single-photon emitters in silicon nitride (SiN) films grown on silicon dioxide substrates. Photophysical analysis reveals bright (>10⁵ counts/s), stable, linearly polarized, and pure quantum emitters in SiN films with a second-order autocorrelation function value at zero time delay g⁽²⁾(0) below 0.2 at room temperature. We suggest that the emission originates from a specific defect center in SiN because of the narrow wavelength distribution of the observed luminescence peak. Single-photon emitters in SiN have the potential to enable direct, scalable, and low-loss integration of quantum light sources with a well-established photonic on-chip platform.

Fig. 1.. Room-temperature SPEs in SiN grown on SiO₂-on-Si substrate.

(A) Confocal PL intensity map of the SiN layer. Confirmed SPEs are indicated with red circles. a.u., arbitrary units. (B) Optical image of the sample with markers prepared by the FIB milling to identify the same area in consecutive measurements. (C) Representative 2 μm by 2 μm AFM micrograph revealing the surface morphology of the SiN film and yielding the rms roughness of 1.5 nm. Scale bar, 1 μm.

Fig. 2.. Purity of single-photon emission in SiN.

(A) Confocal PL map of the SPE. (B) Second-order autocorrelation measurement g⁽²⁾(τ) of the emission, yielding g⁽²⁾(0) of 0.12. (C) Histogram of g⁽²⁾(0) distribution from 130 emitters with a bin size of 0.05.

Fig. 3.. Photophysical characteristics of SPEs in SiN measured at room temperature.

(A) PL spectrum with four Gaussian-fitted line shapes. (B) PL stability measurement showing no obvious blinking or bleaching and a low coefficient of variation CV = 0.05. (C) Saturation curve yielding a saturation power of P_sat = 1.37 mW and intensity I_∞ = 0.22 × 10⁶ counts/s (cps). (D) Polarization diagram of the PL emission I(θ) (measured from another emitter). The data are fitted with acos²(θ)-form fit function, yielding the polarization visibility (I_max − I_min)/(I_max + I_min) of 78%.

Fig. 4.. Spectral analysis of SPEs in SiN.

(A) Representative PL spectrum of an SPE. PL spectra can be well fitted with Gaussian line shapes. Inset: Second-order autocorrelation measurements of the emission from the corresponding emitter. (B) Histogram of the wavelength distribution of 133 emitters with a bin width of 3 nm. (C) Histogram of the distribution of the separation energy ∆E obtained for all peaks resolved in PL spectra. The average separation energy is 100 meV. The bin width is 10 meV.

Fig. 5.. Wavelength-resolved detection of single photons.

(A) Confocal PL map of the SPE. (B) PL spectrum of the selected SPE. The PL spectra measured using different spectral filters (Band Pass BP585/40nm and Long Pass LP633 nm) are normalized and superimposed with the full spectrum (LP550 nm). (C) Second-order autocorrelation measurements g⁽²⁾(τ) of the emission taken using different spectral filters, yielding g⁽²⁾(0) of 0.35 ± 0.05 (top), 0.21 ± 0.11 (middle), and 0.26 ± 0.18 (bottom).