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Register a new userRoom temperature Giant Spin-dependent Photoconductivity in dilute nitride semiconductors
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By combining optical spin injection techniques with transport spectroscopy tools, we demonstrate a spin-photodetector allowing for the electrical measurement and active filtering of conduction band electron spin at room temperature in a non-magnetic GaAsN semiconductor structure. By switching the polarization of the incident light from linear to circular, we observe a Giant Spin-dependent Photoconductivity (GSP) reaching up to 40 % without the need of an external magnetic field. We show that the GSP is due to a very efficient spin filtering effect of conduction band electrons on Nitrogen-induced Ga self-interstitial deep paramagnetic centers.
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Optically addressable spins associated with defects in wide-bandgap semiconductors are versatile platforms for quantum information processing and nanoscale sensing, where spin-dependent inter-system crossing (ISC) transitions facilitate optical spin initialization and readout. Recently, the van der Waals material hexagonal boron nitride (h-BN) has emerged as a robust host for quantum emitters (QEs), but spin-related effects have yet to be observed. Here, we report room-temperature observations of strongly anisotropic photoluminescence (PL) patterns as a function of applied magnetic field for select QEs in h-BN. Field-dependent variations in the steady-state PL and photon emission statistics are consistent with an electronic model featuring a spin-dependent ISC between triplet and singlet manifolds, indicating that optically-addressable spin defects are present in h-BN $-$ a versatile two-dimensional material promising efficient photon extraction, atom-scale engineering, and the realization of spin-based quantum technologies using van der Waals heterostructures.
THz Time-Resolved Photoconductivity is used to probe carrier dynamics in the dilute III-V nitride GaP0.49As0.47N0.036. In these measurements a femtosecond optical pump-pulse excites electron-hole pairs, and a delayed THz pulse measures the change in conductivity. We find the photoconductivity is dominated by localized carriers. The decay of photoconductivity after excitation is consistent with bimolecular electron-hole recombination with recombination constant r = 3.2E-8 +/-0.8E-8 cm3/s. We discuss the implications for applications in solar energy.
Optically active defects in solids with accessible spin states are promising candidates for solid state quantum information and sensing applications. To employ these defects as quantum building blocks, coherent manipulation of their spin state is required. Here we realize coherent control of ensembles of boron vacancy (V$_B^-$) centers in hexagonal boron nitride (hBN). Specifically, by applying pulsed spin resonance protocols, we measure spin-lattice relaxation time ($T_1$) of 18 $mu$s and spin coherence time ($T_2$) of 2 $mu$s at room temperature. The spin-lattice relaxation time increases by three orders of magnitude at cryogenic temperature. Furthermore, employing a two- and three-pulse electron spin-echo envelope modulation (ESEEM) we separate the quadrupole and hyperfine interactions with the surrounding nuclei. Finally, by applying a method to decouple the spin state from its inhomogeneous nuclear environment - a hole-burning - the spectral optically detected magnetic resonance linewidth is significantly reduced to several tens of kHz, thus extending the spin coherence time by a factor of three. Our results are important for employment of van der Waals materials for quantum technologies, specifically in the context of using hBN as a high-resolution quantum sensor for hybrid quantum systems including 2D heterostructures, nanoscale devices and emerging atomically thin magnets.
The optical orientation of the exciton spin in an ensemble of self-organized cubic GaN/AlN quantum dots is studied by time-resolved photoluminescence. Under a polarized quasi-resonant excitation, the luminescence linear polarization exhibits no temporal decay, even at room temperature. This demonstrates the robustness of the exciton spin polarization in these cubic nitride nanostructures, with characteristic decay times longer than 10 ns.
Single-photon emitters are essential for enabling several emerging applications in quantum information technology, quantum sensing and quantum communication. Scalable photonic platforms capable of hosting intrinsic or directly embedded sources of single-photon emission are of particular interest for the realization of integrated quantum photonic circuits. Here, we report on the first-time observation of room-temperature single-photon emitters in silicon nitride (SiN) films grown on silicon dioxide substrates. As SiN has recently emerged as one of the most promising materials for integrated quantum photonics, the proposed platform is suitable for scalable fabrication of quantum on-chip devices. Photophysical analysis reveals bright (>$10^5$ counts/s), stable, linearly polarized, and pure quantum emitters in SiN films with the value of the second-order autocorrelation function at zero time delay $g^{(2)}(0)$ below 0.2 at room temperatures. The emission is suggested to originate from a specific defect center in silicon nitride due to the narrow wavelength distribution of the observed luminescence peak. Single-photon emitters in silicon nitride have the potential to enable direct, scalable and low-loss integration of quantum light sources with the well-established photonic on-chip platform.
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