Here we report on the Ga self-catalyzed growth of near full-composition-range energy-gap-tunable GaAsSb nanowires by molecular-beam epitaxy. GaAsSb nanowires with different Sb content are systematically grown by tuning the Sb and As fluxes, and the As background. We find that GaAsSb nanowires with low Sb content can be grown directly on Si(111) substrates (0 ≤ x ≤ 0.60) and GaAs nanowire stems (0 ≤ x ≤ 0.50) by tuning the Sb and As fluxes. To obtain GaAsSb nanowires with x ranging from 0.60 to 0.93, we grow the GaAsSb nanowires on GaAs nanowire stems by tuning the As background. Photoluminescence measurements confirm that the emission wavelength of the GaAsSb nanowires is tunable from 844 nm (GaAs) to 1760 nm (GaAsSb). High-resolution transmission electron microscopy images show that the grown GaAsSb nanowires have pure zinc-blende crystal structure. Room-temperature Raman spectra reveal a redshift of the optical phonons in the GaAsSb nanowires with x increasing from 0 to 0.93. Field-effect transistors based on individual GaAsSb nanowires are fabricated, and rectifying behavior is observed in devices with low Sb content, which disappears in devices with high Sb content. The successful growth of high-quality GaAsSb nanowires with near full-range bandgap tuning may speed up the development of high-performance nanowire devices based on such ternaries.

Research on hexagonal boron nitride (hBN) has been intensified recently due to the application of hBN as a promising system of single-photon emitters. To date, the single photon origin remains under debate even though many experiments and theoretical calculations have been performed. We have measured the pressure-dependent photoluminescence (PL) spectra of hBN flakes at low temperatures by using a diamond anvil cell device. The absolute values of the pressure coefficients of discrete PL emission lines are all below 15 meV/GPa, which is much lower than the pressure-induced 36 meV/GPa redshift rate of the hBN bandgap. These PL emission lines originate from atom-like localized defect levels confined within the bandgap of the hBN flakes. Interestingly, the experimental results of the pressure-dependent PL emission lines present three different types of pressure responses corresponding to a redshift (negative pressure coefficient), a blueshift (positive pressure coefficient), or even a sign change from negative to positive. Density functional theory calculations indicate the existence of competition between the intralayer and interlayer interaction contributions, which leads to the different pressure-dependent behaviors of the PL peak shift.

Quantum technologies require robust and photostable single-photon emitters. Here, room temperature operated single-photon emissions from isolated defects in aluminum nitride (AlN) films are reported. AlN films were grown on nanopatterned sapphire substrates by metal organic chemical vapor deposition. The observed emission lines range from visible to near-infrared, with highly linear polarization characteristics. The temperature-dependent line width increase shows T3 or single-exponential behavior. First-principle calculations based on density functional theory show that point defect species, such as antisite nitrogen vacancy complex (NAlVN) and divacancy (VAlVN) complexes, are considered to be an important physical origin of observed emission lines ranging from approximately 550 to 1000 nm. The results provide a new platform for on-chip quantum sources.

Single-photon emitters (SPEs) are one of the building blocks in quantum information processing. Here, we report detailed experimental optical properties of the SPEs in aluminum nitride (AlN) films at 10 K. The high-quality AlN films are grown by metal–organic chemical vapor deposition on graphene/sapphire substrates, which can conquer the large lattice and thermal mismatches between the sapphire and AlN. We report the defects in AlN with a relatively high Debye–Waller factor up to ∼29% and near-perfect linear polarization SPEs with a saturation count rate of 1.43 × 106 counts/s. The power-dependent second-order autocorrelation measurements are used to study the transition kinetics, which can be described using a three-level model. The polarization measurements of absorption and emission reveal the optical cycle mechanism, where a particular zero-phonon line may be excited via multiple mechanisms. This work provides some insight into the nature of the optical properties and energy-level structures of AlN defects, which pave the way to integrated on-chip quantum photonics.

Quantum emitters are needed for a myriad of applications ranging from quantum sensing to quantum computing. Hexagonal boron nitride (hBN) quantum emitters are the most promising solid-state platform to date due to its high brightness, stability, and the possibility of spin photon interface. However, the understanding of the physical origins of the single-photon emitters (SPEs) is still limited. Here, we present concrete and conclusive evidence that the dense SPEs in hBN, across entire visible spectrum, can be well explained by donor-acceptor pairs (DAPs). Based on the DAP transition generation mechanism, we have calculated their wavelength fingerprint, matching well with the experimentally observed photoluminescence spectrum. Our work serves as a step forward for the physical understanding of SPEs in hBN and their applications in quantum technologies.

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Dynamic processes of electron transfer by optical doping in monolayer MoSe2 at 6 K are investigated via measuring time resolved photoluminescence (PL) traces under different excitation powers. Time-dependent electron transfer process can be analyzed by a power-law distribution of t −α with α = 0.1–0.24, depending on the laser excitation power. The average electron transfer time of approximately 27.65 s is obtained in the excitation power range of 0.5 to 100 μW. As the temperature increases from 20 to 44 K, the energy difference between the neutral and charged excitons is observed to decrease.

We report on 1.3 μm single-photon emission based on a self-assembled strain-coupled bilayer of InAs quantum dots (QDs) embedded in a micropillar Bragg cavity at temperature of liquid nitrogen or even as high as 120 K. The obtained single-photon flux into the first lens of the collection optics is 4.2 × 106 and 3.3 × 106/s at 82 and 120 K, respectively, corresponding to a second-order correlation function at zero delay times of 0.27(2) and 0.28(3). This work reports on the significant effect of the micropillar cavity-related enhancement of QD emission and demonstrates an opportunity to employ telecom band single-photon emitters at liquid nitrogen or even higher temperature.