GaAs Quantum Dots Research Articles

Tuning the nonlinear optical properties of a 1D excitonic GaAs quantum dot system under a semi-parabolic potential with a detailed comparison with the experimental results: interplay of hydrostatic pressure and temperature

Tuning the nonlinear optical properties of a 1D excitonic GaAs quantum dot system under a semi-parabolic potential with a detailed comparison with the experimental results: interplay of hydrostatic pressure and temperature

Quantitative photothermal investigation of nonradiative recombination parameters in GaAs/InAs(QD)/GaAs quantum dot structures using a three-layer laser beam deflection model

In this paper, we developed a theoretical model for the photothermal deflection technique in order to investigate the electronic parameters of three-layer semiconductor structures. This model is based on the resolution of thermal and photogenerated carrier diffusion-wave equations in different media. Theoretical results show that the amplitude and phase of the photothermal deflection signal is very sensitive to the nonradiative recombination parameters. The theoretical model is applied to one layer of InAs quantum dots (QDs) inserted in GaAs matrix InAs/GaAs QDs in order to investigate the QD density effects on nonradiative recombination parameters in InAs through fitting the theoretical photothermal beam deflection signal to the experimental data. It was found that the minority carrier lifetime and the electronic diffusivity decrease as functions of increasing InAs QD density. This result is also related to the decrease in the mobility from 21.58 to 4.17 (±12.9%) cm2/V s and the minority carrier diffusion length from 0.62 (±5.8%) to 0.14 (±10%) μm, respectively. Furthermore, both interface recombination velocities S2/3 of GaAs/InAs (QDs) and S1/2 of InAs (QDs)/GaAs increase from 477.7 (±6.2%) to 806.5 (±4%) cm/s and from 75 (±7.8%) to 148.1 (±5.5%) cm/s, respectively.

Reductive pathways in molten inorganic salts enable colloidal synthesis of III-V semiconductor nanocrystals.

Colloidal quantum dots, with their size-tunable optoelectronic properties and scalable synthesis, enable applications in which inexpensive high-performance semiconductors are needed. Synthesis science breakthroughs have been key to the realization of quantum dot technologies, but important group III-group V semiconductors, including colloidal gallium arsenide (GaAs), still cannot be synthesized with existing approaches. The high-temperature molten salt colloidal synthesis introduced in this work enables the preparation of previously intractable colloidal materials. We directly nucleated and grew colloidal quantum dots in molten inorganic salts by harnessing molten salt redox chemistry and using surfactant additives for nanocrystal shape control. Synthesis temperatures above 425°C are critical for realizing photoluminescent GaAs quantum dots, which emphasizes the importance of high temperatures enabled by molten salt solvents. We generalize the methodology and demonstrate nearly a dozen III-V solid-solution nanocrystal compositions that have not been previously reported.

Enhanced polarization sensitivity and tunability in truncated pyramidal GaAs quantum dots for FIR applications

The far-infrared (FIR) spectrum, covering wavelengths from 20 to 1000 μm, presents significant challenges for the manipulation and detection of polarized light, especially in the short-wavelength FIR range of 20–100 μm. This study investigates the effectiveness of truncated pyramidal GaAs quantum dots in improving the absorption coefficient of polarized light within this range. Utilizing the finite difference method to obtain numerical solutions of the Schrödinger equation within the adiabatic approximation, we analyze the effects of various base shapes—equilateral hexagon, irregular hexagon, and equilateral triangle—on the optical absorption coefficients when subjected to an electric field with different directions and magnitudes. Our results reveal that triangular pyramidal quantum dots offer enhanced polarization sensitivity and greater tunability of absorption peaks compared to structures with other base shapes. Moreover, the direction of the applied electric field is crucial for tuning the absorption peaks in the desired range of FIR wavelength. These findings demonstrate the potential of truncated pyramidal GaAs quantum dots not only for improving sensing technologies but also for managing electromagnetic interference in advanced communication systems.

Purifying quantum-dot light in a coherent frequency interface

Abstract Quantum networks typically operate in the telecom wavelengths to take advantage of low-loss transmission in optical fibres. However, bright quantum dots (QDs) emitting highly indistinguishable quantum states of light, such as InGaAs QDs, often emit photons in the near infrared thus necessitating frequency conversion (FC) to the telecom band. Furthermore, the signal quality of quantum emissions is crucial for the effective performance of these networks. In this work we report a method for simultaneously implementing spectral purification and frequency shifting of single photons from QD sources to the c-band in a periodically poled lithium niobate waveguide. We consider difference frequency generation in the counter-propagating configuration to implement FC with the output emission bandwidth in units of GHz. Our approach establishes a clear path to integrating high-performance single-emitter sources in a hybrid quantum network.

Tuning the Noise‐Driven Magnetocaloric Effect in Doped GaAs Quantum Dot in View of Tsallis Entropy

AbstractCurrent inspection strives to perform a detailed elaboration of the Tsallis entropy‐based magnetocaloric effect (MCE) of GaAs quantum dot (QD) doped with Gaussian impurity and under applied Gaussian white noise. Noise takes additive and multiplicative pathways for its entry to the doped QD. MCE has been found to decrease following the enhancement of temperature. The enquiry manifests magnetic field‐induced confinement and consequent decline in the disorder of the system during the gradual variation of several physical parameters. However, harnessing the extent of above confinement involves extremely sensitive and delicate control over the resultant influence of the particular physical parameter undergoing change, its range of magnitude, application of noise and its mode of inclusion. Importantly, MCE has been found to maximize only during the change in the strength of the dopant potential under multiplicative noise. And, on most occasions, multiplicative noise profoundly raises the MCE over its value under the state devoid of noise and under additive noise.

Tailoring the magnetocaloric effect in doped GaAs quantum dot under the influence of noise

Present inspection thoroughly explores the magnetocaloric effect (MCE) of GaAs quantum dot (QD) doped with Gaussian impurity and under the influence of Gaussian white noise (GWHN). Two different routes for the application of GWHN viz. additive and multiplicative have been considered. The enquiry highlights extremely subtle and complex interplay between temperature, GWHN, mode of entry of GWHN and the given physical parameters concerned that finally designs the MCE profiles. The fact that under certain conditions the MCE maximizes comes out to be technologically relevant. Deviations in the MCE profiles from the noise-free state appear to be more profound under multiplicative noise than its additive analogue. As a general trend, additive and multiplicative noise reduces and augments the MCE, respectively, from that under the noise-free situation.

Role of confinement shape and spin-orbit interactions on binding energy, temperature, transition energy, susceptibility and oscillator strength of an off-center [formula omitted] impurity in a GaAs quantum dot

This study explores the influence of confinement potential shape on the behavior of an off-center D0 impurity in a quantum dot (QD). In this study, we use the power exponential potential and Rashba spin-orbit interaction (RSOI), and Dresselhaus spin-orbit interaction (DSOI) beside an external magnetic field. Employing the variational method, we obtained the ground and first excited state energies and corresponding binding energies, transition energy, and magnetic susceptibilities across various impurity positions, QD parameters, and potential shapes. We ascertain the stable temperature by equating the maximum binding energy of an off-center D0 system. Subsequently, we computed the oscillator strength (OS) and conducted a comparative analysis with existing literature. Our findings demonstrate an exciting behavior in response to changes in potential shape, QD parameters, and spin-orbit coupling strengths. It helps us better understand how an off-center impurity behaves with different potential shapes in QDs and helps engineers to design devices in spintronics.

Laser-induced spectral tuning of single quantum dots embedded into microposts cladded with HfO2

Our work investigates the precise tuning of InGaAs quantum dots (QDs) embedded into microposts by leveraging HfO2 crystallization-induced micro-strain via laser annealing. We investigate the efficacy of laser annealing power as a parameter for spectral control, achieving a notable blue shift of QD emissions of up to 5 meV. Through comprehensive Raman thermometry, we reveal consistent dependencies in laser-induced heating relative to micropost diameter, with larger microposts exhibiting superior heat dissipation capabilities and smaller tuning range. For instance, a 5.0 μm micropost demonstrates a maximum local temperature increase of 260 K at 1.82 mW of annealing power, compared to 435 K for a 1.1 μm diameter micropost under the same conditions. By correlating local temperatures derived from the longitudinal optical phonon linewidth of the Raman spectra, with QD emission line blue shift at specific laser powers, the tunability across differing post diameters is studied. Our findings underscore the potential of strain-tuning QDs through laser-induced HfO2 crystallization, offering avenues for scalable resonant single-photon sources applicable in superradiance and multi-photon interference scenarios.

Feasibility of All Single-Qubit Gates with Four InGaAs Quantum Dots Coupled to Two Silver Nanowires

Feasibility of All Single-Qubit Gates with Four InGaAs Quantum Dots Coupled to Two Silver Nanowires

A source of entangled photons based on a cavity-enhanced and strain-tuned GaAs quantum dot

A quantum-light source that delivers photons with a high brightness and a high degree of entanglement is fundamental for the development of efficient entanglement-based quantum-key distribution systems. Among all possible candidates, epitaxial quantum dots are currently emerging as one of the brightest sources of highly entangled photons. However, the optimization of both brightness and entanglement currently requires different technologies that are difficult to combine in a scalable manner. In this work, we overcome this challenge by developing a novel device consisting of a quantum dot embedded in a circular Bragg resonator, in turn, integrated onto a micromachined piezoelectric actuator. The resonator engineers the light-matter interaction to empower extraction efficiencies up to 0.69(4). Simultaneously, the actuator manipulates strain fields that tune the quantum dot for the generation of entangled photons with corrected fidelities to a maximally entangled state up to 0.96(1). This hybrid technology has the potential to overcome the limitations of the key rates that plague QD-based entangled sources for entanglement-based quantum key distribution and entanglement-based quantum networks.

Metrological characterization of a commercial single-photon source with high photon flux emission

We present a comprehensive metrological characterization of a commercial single-photon source with high photon flux emission for use in radiometry. The source is based on an InGaAs quantum dot in a micropillar. A comparative analysis of two excitation schemes—phonon-assisted excitation and two-photon excitation—explores differences in excitation power dependence, temporal stability and single-photon purity. The commercial source exhibits excellent properties for the field of quantum radiometry, achieving simultaneously a photon flux of (17.19 ± 0.09) million photons/s for a pulse repetition rate of 79.4 MHz, and a single-photon purity of 98%. Its optical power of (3.68 ± 0.02) pW is directly determined with a traceably calibrated low-noise photodiode. The ability to directly compare the photocurrent in a low-noise photodiode with the count rate at a single-photon avalanche detector allows for a seamless transition between the classical and quantum realizations of optical power. Therefore, we were able to build another bridge between classical and quantum radiometry by using a deterministic single-photon source.

InGaAs quantum dot chains grown by twofold selective area molecular beam epitaxy

Increasing quantum confinement in semiconductor quantum dot (QD) systems is essential to perform robust simulations of many-body physics. By combining molecular beam epitaxy and lithographic techniques, we developed an approach consisting of a twofold selective area growth to build QD chains. Starting from 15 nm-thick and 65 nm-wide in-plane In0.53Ga0.47As nanowires on InP substrates, linear arrays of In0.53Ga0.47As QDs were grown on top, with tunable lengths and separations. Kelvin probe force microscopy performed at room temperature revealed a change of quantum confinement in chains with decreasing QD sizes, which was further emphasized by the spectral shift of quantum levels resolved in the conduction band with low temperature scanning tunneling spectroscopy. This approach, which allows the controlled formation of 25 nm-thick QDs with a minimum length and separation of 30 nm and 22 nm respectively, is suitable for the construction of scalable fermionic quantum lattices.

Wavelength-tunable high-fidelity entangled photon sources enabled by dual Stark effects

The construction of a large-scale quantum internet requires quantum repeaters containing multiple entangled photon sources with identical wavelengths. Semiconductor quantum dots can generate entangled photon pairs deterministically with high fidelity. However, realizing wavelength-matched quantum-dot entangled photon sources faces two difficulties: the non-uniformity of emission wavelength and exciton fine-structure splitting induced fidelity reduction. Typically, these two factors are not independently tunable, making it challenging to achieve simultaneous improvement. In this work, we demonstrate wavelength-tunable entangled photon sources based on droplet-etched GaAs quantum dots through the combined use of AC and quantum-confined Stark effects. The emission wavelength can be tuned by ~1 meV while preserving an entanglement fidelity f exceeding 0.955(1) in the entire tuning range. Based on this hybrid tuning scheme, we finally demonstrate multiple wavelength-matched entangled photon sources with f > 0.919(3), paving the way towards robust and scalable on-demand entangled photon sources for quantum internet and integrated quantum optical circuits.

Modulation of Thermodynamic Properties of Doped GaAs Quantum Dot under the Influence of Noise

In the present enquiry, an in‐depth analysis of internal energy, entropy, heat capacity, and Helmholtz free energy of GaAs quantum dot (QD) which contains Gaussian impurity as dopant and falls under the influence of applied Gaussian white noise (GWHN) is performed. GWHN takes additive and multiplicative routes for its entrance to the doped QD. In this study, highly delicate and complex interplay between temperature, presence/absence of GWHN, mode of incorporation of GWHN, and the particular physical parameters concerned is unveiled. The said interplay, in effect, designs the features of the thermal properties. The enquiry uncovers competitive behavior between thermal disorder and spatial disorder that also affects the said thermodynamic properties.

Calculation and design of GaAs quantum dot devices where the vibrational modes can be frozen out at cryogenic temperatures

We calculate how the frequencies of the vibrational modes in a free-standing GaAs bar are changed as a function of the bar’s geometrical features such as length, thickness and shape. After understanding the effect of the physical characteristics we add finger gates that will be used to define quantum dots on the bar and study the system as a function of the length of the suspended finger gates, and their material properties. Finally, we strengthen the bridges in order that the first vibrational modes occur at a temperature of 100 mK or more, so that all modes can be frozen out when operated in a dilution refrigerator.

Effect of rainbow gravity, PDM, and external magnetic field on optical properties and energy spectra of GaAs quantum dot

Effect of rainbow gravity, PDM, and external magnetic field on optical properties and energy spectra of GaAs quantum dot

Reduction of GaAs Buffer Thickness and Its Impact on Epitaxially Integrated III-V Quantum Dot Lasers on a Si Substrate.

Monolithic integration of III-V quantum dot (QD) lasers onto a Si substrate is a scalable and reliable approach for obtaining highly efficient light sources for Si photonics. Recently, a combination of optimized GaAs buffers and QD gain materials resulted in monolithically integrated butt-coupled lasers on Si. However, the use of thick GaAs buffers up to 3 μm not only hinders accurate vertical alignment to the Si optical waveguide but also imposes considerable growth costs and time constraints. Here, for the first time, we demonstrate InAs QD lasers epitaxially grown on a 700 nm thick GaAs/Si template, which is approximately four times thinner than the conventional III-V buffers on Si. The optimized 700 nm GaAs buffer yields a remarkably smooth surface and low threading dislocation density of 4 × 108 cm-2, which is sufficient for QD laser growth. The InAs QD lasers fabricated on these ultrathin templates still lase at room temperature with a threshold current density of 661 A/cm2 and a characteristic temperature of 50 K. We believe that these results are important for the monolithically integrated III-V QD lasers for Si photonics applications.

Analyzing the magnetocaloric effect in doped GaAs quantum dot in view of Shannon entropy: role of noise

Analyzing the magnetocaloric effect in doped GaAs quantum dot in view of Shannon entropy: role of noise

Harnessing the Shannon Entropy‐Based Magnetocaloric Effect in GaAs Quantum Dot under the Influence of Noise‐Anharmonicity Interplay

Harnessing the Shannon Entropy‐Based Magnetocaloric Effect in GaAs Quantum Dot under the Influence of Noise‐Anharmonicity Interplay