AlGaAs Nanowires Research Articles

Model of a GaAs Quantum Dot in a Direct Band Gap AlGaAs Wurtzite Nanowire.

We present a study with a numerical model based on k→·p→, including electromechanical fields, to evaluate the electromechanical and optoelectronic properties of single GaAs quantum dots embedded in direct band gap AlGaAs nanowires. The geometry and the dimensions of the quantum dots, in particular the thickness, are obtained from experimental data measured by our group. We also present a comparison between the experimental and numerically calculated spectra to support the validity of our model.

Синтез методом молекулярно-пучковой эпитаксии и свойства InAs-квантовых точек в теле AlGaAs нитевидных нанокристаллов

We present the results of experimental studies on the synthesis by molecular-beam epitaxy of AlGaAs nanowires with InAs quantum dots. The morphological, structural, and optical properties of the grown nanostructures have been studied. It is important to note that the emission from quantum dots is observed in the wavelength range from 750 to 970 nm. Assumptions about the nature of short-wavelength emission from quantum dots are formulated. In particular, one of the reasons may be a significant desorption of indium atoms and the presence of gallium atoms in catalyst drops during the growth at a substrate temperature of 510◦C. The proposed technology opens up new possibilities for integration direct-gap III−V materials with a silicon platform for various applications in photonics and quantum communications.

Особенности структуры поверхности и поверхностного электронного транспорта в коррелированном топологическом изоляторе SmB-=SUP=-VI-=/SUP=-

We present the results of experimental studies on the synthesis by molecular-beam epitaxy of AlGaAs nanowires with InAs quantum dots. The morphological, structural, and optical properties of the grown nanostructures have been studied. It is important to note that the emission from quantum dots is observed in the wavelength range from 750 to 970 nm. Assumptions about the nature of short-wavelength emission from quantum dots are formulated. In particular, one of the reasons may be a significant desorption of indium atoms and the presence of gallium atoms in catalyst drops during the growth at a substrate temperature of 510◦C. The proposed technology opens up new possibilities for integration direct-gap III−V materials with a silicon platform for various applications in photonics and quantum communications.

Inducing Strong Light-Matter Coupling and Optical Anisotropy in Monolayer MoS2 with High Refractive Index Nanowire.

Mixed-dimensional heterostructures combine the merits of materials of different dimensions; therefore, they represent an advantageous scenario for numerous technological advances. Such an approach can be exploited to tune the physical properties of two-dimensional (2D) layered materials to create unprecedented possibilities for anisotropic and high-performance photonic and optoelectronic devices. Here, we report a new strategy to engineer the light–matter interaction and symmetry of monolayer MoS2 by integrating it with one-dimensional (1D) AlGaAs nanowire (NW). Our results show that the photoluminescence (PL) intensity of MoS2 increases strongly in the mixed-dimensional structure because of electromagnetic field confinement in the 1D high refractive index semiconducting NW. Interestingly, the 1D NW breaks the 3-fold rotational symmetry of MoS2, which leads to a strong optical anisotropy of up to ∼60%. Our mixed-dimensional heterostructure-based phototransistors benefit from this and exhibit an improved optoelectronic device performance with marked anisotropic photoresponse behavior. Compared with bare MoS2 devices, our MoS2/NW devices show ∼5 times enhanced detectivity and ∼3 times higher photoresponsivity. Our results of engineering light–matter interaction and symmetry breaking provide a simple route to induce enhanced and anisotropic functionalities in 2D materials.

Formation of InGaAs quantum dots in the body of AlGaAs nanowires via molecular-beam epitaxy

The results of experimental studies on the synthesis by molecular-beam epitaxy of AlGaAs nanowires with InGaAs quantum dots are presented. It was shown that, as in the case of the InP/InAsP material system, the formation of predominantly two objects is observed in the body of AlGaAs nanowire: InGaAs quantum dot due to axial growth and InGaAs quantum well due to radial growth. It is important to note that the grown nanostructures were formed predominantly in the wurtzite crystallographic phase. The results of the grown nanostructures physical properties studies indicate that they are promising for moving single-photon sources to the long-wavelength region. The proposed technology opens up new possibilities for integration direct-gap III-V materials with a silicon platform for various applications in photonics and quantum communications. Keywords: semiconductors, nanowires, quantum dots, III-V compounds, silicon, molecular-beam epitaxy.

Формирование InGaAs-квантовых точек в теле AlGaAs-нитевидных нанокристаллов при молекулярно-пучковой эпитаксии

The results of experimental studies on the synthesis by molecular-beam epitaxy of AlGaAs nanowires with InGaAs quantum dots are presented. It was shown that, as in the case of the InP/InAsP material system, the formation of predominantly two objects is observed in the body of AlGaAs nanowire: InGaAs quantum dot due to axial growth and InGaAs quantum well due to radial growth. It is important to note that the grown nanostructures were formed predominantly in the wurtzite crystallographic phase. The results of the grown nanostructures physical properties studies indicate that they are promising for moving single-photon sources to the long-wavelength region. The proposed technology opens up new possibilities for integration direct-gap III−V materials with a silicon platform for various applications in photonics and quantum communications.

III-V nanostructures with different dimensionality on silicon

The possibility of AlGaAs nanowires with GaAs quantum dots and InP nanowires with InAsP quantum dots growth by molecular-beam epitaxy on silicon substrates has been demonstrated. Results of GaAs quantum dots optical properties studies have shown that these objects are sources of single photons. In case of InP nanowires with InAsP quantum dots, the results we obtained indicate that nearly 100% of coherent nanowires can be formed with high optical quality of this system on a silicon surface. The presence of a band with maximum emission intensity near 1.3 μm makes it possible to consider the given system promising for further integration of optical elements on silicon platform with fiber-optic systems. Our work, therefore, opens new prospects for integration of direct bandgap semiconductors and singlephoton sources on silicon platform for various applications in the fields of silicon photonics and quantum information technology.

Formation of Hexagonal Germanium on AlGaAs Nanowire Surfaces by Molecular-Beam Epitaxy

Formation of Hexagonal Germanium on AlGaAs Nanowire Surfaces by Molecular-Beam Epitaxy

Formation of Hexagonal Ge Stripes on the Side Facets of AlGaAs Nanowires: Implications for Near-Infrared Detectors

Obtaining hexagonal Ge is a great challenge and has previously been achieved by transferring the wurtzite phase of GaAs nanowires, where Ge forms a conformal shell around a nanowire. Here, we demonstrate hexagonal Ge stripes of 6 nm height and 17 nm width, which decorate 25 nm-wide side facets of wurtzite AlGaAs nanowires. Ge shells are grown by molecular beam epitaxy at a low temperature of 320 °C. The hexagonal structure of Ge is revealed by Raman spectroscopy and high-resolution transmission electron microscopy (TEM), the latter shows the pure 2H phase. The formation of Ge stripes on the side facets of AlGaAs nanowires is demonstrated by scanning TEM in the angular annular dark-field mode and explained within an energetic model. These results show a possibility of forming 2H wire-like Ge structures with tunable geometry using AlGaAs nanowire templates. Such structures can be exploited for direct band gap engineering and quantum confinement effects and used in near-infrared optoelectronics based on nanostructured Ge.

Self-Catalyzed AlGaAs Nanowires and AlGaAs/GaAs Nanowire-Quantum Dots on Si Substrates.

Self-catalyzed AlGaAs nanowires (NWs) and NWs with a GaAs quantum dot (QD) were monolithically grown on Si(111) substrates via solid-source molecular beam epitaxy. This growth technique is advantageous in comparison to the previously employed Au-catalyzed approach, as it removes Au contamination issues and renders the structures compatible with complementary metal–oxide–semiconductor (CMOS) technology applications. Structural studies reveal the self-formation of an Al-rich AlGaAs shell, thicker at the NW base and thinning towards the tip, with the opposite behavior observed for the NW core. Wide alloy fluctuations in the shell region are also noticed. AlGaAs NW structures with nominal Al contents of 10, 20, and 30% have strong room temperature photoluminescence, with emission in the range of 1.50–1.72 eV. Individual NWs with an embedded 4.9 nm-thick GaAs region exhibit clear QD behavior, with spatially localized emission, both exciton and biexciton recombination lines, and an exciton line width of 490 μeV at low temperature. Our results demonstrate the properties and behavior of the AlGaAs NWs and AlGaAs/GaAs NWQDs grown via the self-catalyzed approach for the first time and exhibit their potential for a range of novel applications, including nanolasers and single-photon sources.

Directional Radiation from GaAs quantum dots in AlGaAs nanowires

Directional Radiation from GaAs quantum dots in AlGaAs nanowires

XXV Международный симпозиум Нанофизика и наноэлектроника", Нижний Новгород, 9-12 марта 2021 г. Формирование гексагональной фазы германия на поверхности нитевидных нанокристаллов AlGaAs методом молекулярно-пучковой эпитаксии

Experimental results of studying the germanium deposition on the surface of AlGaAs nanowires are presented. The formation of both cubic and hexagonal Ge phases was revealed using Raman spectroscopy. The inheritance of the crystal structure during the growth of thin germanium layers on the lateral surfaces of wurtzite nanowires was shown.

Направленное излучение из квантовых точек GaAs в теле нитевидных нанокристаллов AlGaAs

We present the results on experimental studies of the directional radiation from GaAs quantum dots in AlGaAs nanowires grown by molecular beam epitaxy technique on silicon surface. It was shown that the radiation intensity from GaAs quantum dots in the direction of nanowires growth is 2 orders of magnitude higher than the intensity of radiation in the perpendicular direction.

Multiply GaAs quantum dots in AlGaAs nanowires: MBE growth and properties

A possibility of the AlGaAs nanowires with multiply GaAs QDs MBE growth on silicon substrates has been demonstrated. The morphological on optical properties of grown structures were studied.

Resonant excitation of nanowire quantum dots

GaAs quantum dots in nanowires are one of the most promising candidates for scalable quantum photonics. They have excellent optical properties, can be frequency-tuned to atomic transitions, and offer a robust platform for fabrication of multi-qubit devices that promise to unlock the full technological potential of quantum dots. Coherent resonant excitation is necessary for virtually any practical application because it allows, for instance, for on-demand generation of single and entangled photons, photonic clusters states, and electron spin manipulation. However, emission from nanowire structures under this excitation scheme has never been demonstrated. Here we show, for the first time, biexciton–exciton cascaded emission via resonant two-photon excitation and resonance fluorescence from an epitaxially grown GaAs quantum dot in an AlGaAs nanowire. We also report that resonant excitation schemes, combined with above-bandgap excitation, can be used to clean and enhance the emission of nanowire quantum dots.

Hybrid AlGaAs nanowires on silicon: growth and properties

In the article, we demonstrate the growth of AlGaAs nanowires on silicon substrates. It is shown that a controlled growth of short GaAs insertions inside AlGaAs nanowires is possible. Optically, such segments shows sharp and intense quantum dot - like emission lines. Our work opens new prospects for integration of direct bandgap semiconductors and single-photon sources on silicon platform for various applications in the fields of silicon photonics and quantum information technology.

Structal and Optical Properties Algaas Nanowires Grown by Mbe on Si(111) Substrate

In this work, we present the results of photoluminescence measurements of wurtzite AlGaAs nanowires, coupled with the transmission electron microscopy structural analysis. AlGaAs NWs were grown by molecular beam epitaxy under the nominal aluminum content of 0.3 - 0.8. The results of TEM measurements demonstrated wurtzite crystal structure of AlGaAs nanowires.

Strong Modulations of Optical Reflectance in Tapered Core-Shell Nanowires.

Random assemblies of vertically aligned core–shell GaAs–AlGaAs nanowires displayed an optical response dominated by strong oscillations of the reflected light as a function of the incident angle. In particular, angle-resolved specular reflectance measurements showed the occurrence of periodic modulations in the polarization-resolved spectra of reflected light for a surprisingly wide range of incident angles. Numerical simulations allowed for identifying the geometrical features of the core–shell nanowires leading to the observed oscillatory effects in terms of core and shell thickness as well as the tapering of the nanostructure. The present results indicate that randomly displaced ensembles of nanoscale heterostructures made of III–V semiconductors can operate as optical metamirrors, with potential for sensing applications.

Nanowire Quantum Dots Tuned to Atomic Resonances.

Quantum dots tuned to atomic resonances represent an emerging field of hybrid quantum systems where the advantages of quantum dots and natural atoms can be combined. Embedding quantum dots in nanowires boosts these systems with a set of powerful possibilities, such as precise positioning of the emitters, excellent photon extraction efficiency and direct electrical contacting of quantum dots. Notably, nanowire structures can be grown on silicon substrates, allowing for a straightforward integration with silicon-based photonic devices. In this work we show controlled growth of nanowire-quantum-dot structures on silicon, frequency tuned to atomic transitions. We grow GaAs quantum dots in AlGaAs nanowires with a nearly pure crystal structure and excellent optical properties. We precisely control the dimensions of quantum dots and their position inside nanowires and demonstrate that the emission wavelength can be engineered over the range of at least 30 nm around 765 nm. By applying an external magnetic field, we are able to fine-tune the emission frequency of our nanowire quantum dots to the D2 transition of 87Rb. We use the Rb transitions to precisely measure the actual spectral line width of the photons emitted from a nanowire quantum dot to be 9.4 ± 0.7 μeV, under nonresonant excitation. Our work brings highly desirable functionalities to quantum technologies, enabling, for instance, a realization of a quantum network, based on an arbitrary number of nanowire single-photon sources, all operating at the same frequency of an atomic transition.

Low‐Power Continuous‐Wave Second Harmonic Generation in Semiconductor Nanowires

AbstractSemiconductor nanowires (NWs) are promising for realizing various on‐chip nonlinear optical devices, due to their nanoscale lateral confinement and strong light–matter interaction. However, high‐intensity pulsed pump lasers are typically needed to exploit their optical nonlinearity because light couples poorly with nanometric‐size wires. Here, microwatts continuous‐wave light pumped second harmonic generation (SHG) in AlGaAs NWs is demonstrated by integrating them with silicon planar photonic crystal cavities. Light–NW coupling is enhanced effectively by the extremely localized cavity mode at the subwavelength scale. Strong SHG is obtained even with a continuous‐wave laser excitation with a pump power down to W, and the cavity‐enhancement factor is estimated around 150. Additionally, in the integrated device, the NW's SHG is more than two orders of magnitude stronger than third harmonic generations in the silicon slab, though the NW only couples with less than 1% of the cavity mode. This significantly reduced power requirement of NW's nonlinear frequency conversion would promote NW‐based building blocks for nonlinear optics, especially in chip‐integrated coherent light sources, entangled photon pairs and signal processing devices.