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In general, studying the physical properties of low-dimensional systems is one of the urgent problems of modern physics. It is known that the profiles of real low-dimensional systems are not simple, they have a complex quantum hole, so it is very important to study their thermodynamic and kinetic properties. An analytical expression is obtained for the energy spectrum and the density of states of electrons in a quantum well with the potential U = U0ctg² (πz/L), which in limiting cases transforms into energy spectra and densities of states for models of an infinitely deep well and harmonic the oscillator. For this purpose, it is of particular interest to establish the profiles of quantum holes in thin films, calculate the energy spectrum, wave function and density of state function, and investigate the dependence of the density of state function on the potential of the quantum hole. For this reason, the theoretical investigation of physical phenomena in layers with quantum wells of complex shape is of special interest and importance. Such studies, in turn, contribute to the development of new fields in the theory of transfer phenomena in low-dimensional electronic systems. The results obtained in the reviewed work allow the creation of more promising quantum holes with the help of the molecular-beam epitaxy method. The dependence of the density of states on energy for various semiconductor quantum wells is constructed. [ABSTRACT FROM AUTHOR]

Ultraviolet photodetectors (UPDs) based on low‐dimensional halide perovskites have undergone rapid development. Here, regulation of the electronic configuration of low‐dimensional hybrid perovskites are reported via organic cations for self‐powered UPDs. For the first time, it is determine that the rational design of organic cation phenyl alkylammonium can effectively prevent phonon scattering thus increasing charge carrier extraction in low dimensional lead chlorine perovskite thin‐films. As a result, the exciton‐binding energy can be reduced to 62.91 meV in (PMA)2PbCl4 perovskite films with a charge‐carrier mobility of 0.335 cm2 V−1 s−1. The fabricated (PMA)2PbCl4‐based self‐powered UPDs has achieved a high detectivity of 6.32 × 1013 jones with a low noise current of 0.35 pA Hz−1/2 under zero bias. A further demonstration of images with high UV to visible light rejection ratio under weak‐light illumination of 70 nW cm−2 highlights the feasible potential application of low‐dimensional perovskite. [ABSTRACT FROM AUTHOR]

Numerical and analytical results of a study of the single-particle entropy of a quasi-two-dimensional electron gas with allowance for the nonparabolicity of the dispersion are presented. The dependence of the single-particle entropy on the chemical potential of the gas at and far from the resonance points is analysed. It is shown that at low temperatures, the nonparabolicity of the band gives a small correction to the single-particle entropy. Both at and far from the resonance point, this correction is proportional to the product of the nonparabolicity coefficient and temperature α T. The influence of the broadening of the size quantization levels on the single-particle entropy is estimated numerically. The results obtained are presented for different temperatures of the degree of nonparabolicity of the conduction band and the magnitude of broadening. [ABSTRACT FROM AUTHOR]

This paper explores the propagation loss in waveguides on directly bonded InP/Si substrates, using numerical simulations to understand the effect of voids within the waveguide structure. Using COMSOL Multiphysics, we developed a model to simulate light propagation, focusing on how void characteristics such as diameter and angle influence the propagation loss. Our findings reveal a correlation between void dimensions and the increased threshold current density in separate confinement heterostructure multiple quantum well laser diodes, thereby providing insights into optimizing waveguide design for enhanced laser performance on InP/Si substrates. This research underscores the critical role of substrate bonding quality in minimizing internal losses and improving device efficiency. [ABSTRACT FROM AUTHOR]

We propose an original design for a HgCdTe-based terahertz vertical-cavity surface-emitting laser with twenty 5 nm HgTe quantum wells. Feasibility of laser generation at 9 THz and a lattice temperature of 8 K is shown. The estimate of the threshold pump intensity using laser radiation at a wavelength of 5 μm is 3 W/cm2, which makes it possible to expect continuous wave (CW) mode lasing. Such a low required pump intensity will make it possible to create a very compact system of a laser pumped by CW mid-infrared quantum cascade laser. [ABSTRACT FROM AUTHOR]

This study presents a quantum well model using the transfer matrix technique to analyze the charge transfer characteristics of nanostructure sequences in both DNA and superlattices. The unconfined state, or unbound state, above the quantum well is used to investigate carrier behaviors in a semiconductor nanostructure. These analytical approaches can be extended to enhance the understanding of charge transfer in DNA nanostructures with periodic and aperiodic sequences. Experimental validation was conducted through photoreflectance spectroscopy on nanostructures within the semiconductor superlattices. Furthermore, the study's findings were compared with earlier research by Li et al. on the thermoelectric effect and its dependence on molecular length and sequences in single DNA molecules. The results showed agreement, offering novel insights into charge transfer and transport in DNA nanostructures across various sequence types. [ABSTRACT FROM AUTHOR]

The numerical and analytical results of a study on the paramagnetism of a two-dimensional electron gas depending on concentration and temperature are presented. The dependence of spin susceptibility on the width of the quantum well, temperature, concentration, and chemical potential at the resonance points and away from it was analyzed. The susceptibility was analyzed in the model of an ideal gas with a parabolic spectrum and a quantum well of infinite depth. The numerical results of the susceptibility calculation will be presented in graphs for different temperatures, quantum well widths, and concentrations. [ABSTRACT FROM AUTHOR]

The inner barrier in stepped quantum wells, which embrace an intrinsic structural inversion asymmetry (SIA), offers more possibilities for the multi-band spin–orbit (SO) control. By varying the inner band offset δ , which adjusts the quantum confinement for electrons and also the SIA, we reveal that both the Rashba ( α ν ) and Dresselhaus ( β ν ) SO coeffcients of the two subbands exhibit contrasting dependence on δ. Also, α 1 and α 2 may have opposite signs, depending on the value of δ. By fine tuning the inner offset, there may even exist a scenario in which α 2 identically vanishes but α 1 is finite, offering a knob on how to subband-selectively suppress spin relaxation induced by SO coupling. In addition, by resorting to an external gate V g , we reveal that in the regime of α 1 and α 2 having opposite signs, their magnitudes also vary with V g in an opposite manner. This, together with the engineered inner barrier of stepped wells, will facilitate flexible spin manipulation. Finally, the interband SO couplings, which depend on the spatial overlap of wave functions of distinct subbands and the corresponding parities, are also discussed. [ABSTRACT FROM AUTHOR]

Antimonide semiconductor lasers are ideal light sources in the 2–5 μm band, and antimonide type I quantum well semiconductor lasers are represented by the InGaAsSb/AlGaAsSb quantum well material system. In this article, we focus on the epitaxial growth of GaSb-based type I InGaAsSb/AlGaAsSb quantum well materials and their structural and luminescent properties. By changing the thicknesses of the InGaAsSb and AlGaAsSb potential well layers, we investigated the effects of changes in structural parameters and luminescence wavelengths. Altimately, we obtained the materials with good crystalline quality, structural and luminescence properties, providing a good basis for the growth of Type I InGaAsSb/AlGaAsSb quantum well materials. [ABSTRACT FROM AUTHOR]

In this work, a new laterally double diffused metal oxide semiconductor (LDMOS) using In0.53Ga0.47As/In0.52Al0.48As Quantum well (QW) layer with a p-well step gate has been proposed. In the proposed device structure, the gate region splits into three steps in which the oxide thickness increases from the source to the drain end. As the gate insulator width varies from source to drain end, it results in better control of the gate over the channel and also a reduction in the gate-to-drain capacitance (CGD). These features offer higher transconductance with reduced switching delays, which makes the device appropriate for RF applications. Again, the concentration of current in the channel section is enhanced due to the presence of the Quantum well region and the InP spacer layer, which drastically reduces the On-resistance. But, the device achieves lesser gate-to-drain capacitance which results in decrease in the switching speed. On the other hand the proposed device offers less gate charge with the low value of CGD gives minimised switching loss. Based on 2D TCAD simulation, the proposed QW LDMOS exhibits 70% improvement in On-resistance, 45% in breakdown voltage, 84% improvement in peak transconductance, 26% improvement in switching delay, and 19% improvement in gate charge density as compared to conventional In0.53Ga0.47As devices. [ABSTRACT FROM AUTHOR]

In this work, the dependence of the oscillation of the combined density of states on a strong magnetic field in heterostructures based on a rectangular quantum well is studied. The effect of a quantizing magnetic field on the temperature dependence of the combined density of states in nanoscale straight-band heterostructures is investigated. A new mathematical model has been developed for calculating the temperature dependence of the two-dimensional combined density of quantum well states in quantizing magnetic fields. The proposed model explains the experimental results in nanoscale straight-band semiconductors with a parabolic dispersion law. [ABSTRACT FROM AUTHOR]

In this work, the influence of two-dimensional state density on oscillations of transverse electrical conductivity in heterostructures with rectangular quantum wells is investigated. A new analytical expression is derived for calculating the temperature dependence of the transverse electrical conductivity oscillation and the magnetoresistance of a quantum well. For the first time, a mechanism has been developed for oscillating the transverse electrical conductivity and magnetoresistance of a quantum well from the first-order derivative of the magnetic field (differential) ∂ (ρ ⊥ 2 d (E , B , T , d)) ∂ B at low temperatures and weak magnetic fields. The oscillations of electrical conductivity and magnetoresistance of a narrow-band quantum well with a nonparabolic dispersion law are investigated. The proposed theory investigated the results of experiments of a narrow-band quantum well (InxGa 1 − x Sb). [ABSTRACT FROM AUTHOR]

This review paper presents an overview of the optical characterization techniques for Indium Gallium Nitride (InGaN) quantum well (QW) structures at a nanoscale. The two major techniques are reviewed—Electron Microscopy‐Cathodoluminescence (EM‐CL) and Scanning Near‐field Optical Microscopy (SNOM). It elucidates the critical role these methodologies play in revealing the complex properties of InGaN QWs, including their structural characteristics, optical properties, carrier dynamics, and the effects of defects and doping. The review highlights key findings from a variety of studies, demonstrating how EM‐CL and SNOM have contributed to the understanding of these micro‐/nano‐ structures and their potential applications in high‐efficiency optoelectronic devices. [ABSTRACT FROM AUTHOR]

A Silicon Photonics modulator is a high-speed photonic integrated circuit for optical data transmission in high-capacity optical networks. Silicon Photonics modulators in the configuration of a Mach–Zehnder interferometer, in which a PN-junction rib-waveguide phase shifter is inserted in each arm of the interferometer, are studied in this paper because of their superior performance of high-quality optical data generation in a wide range of spectral bands and their simplicity in fabrication processes suitable to production in foundries. Design, fabrication, and fundamental characteristics of Silicon Photonics Mach–Zehnder modulators are reviewed as an introduction to these high-speed PICs on the Silicon Photonics platform. Modulation speed, or modulation bandwidth, is a key performance item, as well as optical loss, in the application to high-speed optical transmitters. Limiting factors on modulation speed are addressed in equations. Electrical resistance–capacitance coupling, which causes optical modulation bandwidth–optical loss trade-off, is the most challenging limiting factor that limits high-speed modulation. Expansion of modulation bandwidth is not possible without increasing optical loss in the conventional approaches. A new idea including quantum-mechanical effect in the design of Silicon Photonics modulators is proposed and proved in computational analysis to resolve the bandwidth loss trade-off. By adding high-mobility quantum-well overlayers to the side slab wings of the rib-waveguide phase shifter, the modulation bandwidth is doubled without increasing optical loss to achieve a 200 Gbaud modulation rate. [ABSTRACT FROM AUTHOR]

Reflection spectra of a heterostructure with a GaAs/AlGaAs quantum well (QW) of 30 nm wide have been studied under additional optical excitation in an external electric field. The influence of the electric field on all parameters of light-hole and heavy-hole exciton resonances, was studied upon selective excitation of various optical transitions. The effect of compensating for the Stark shift upon excitation to the ground exciton state of the QW is found. A sharp increase in the Stark shift of excitons in QW was found upon optical creation of charge carriers in the GaAs buffer layer. A microscopic calculation of exciton states in various electric fields has been performed. A comparison of the calculated and measured Stark shift of the heavy-hole exciton is used to obtain the dependence of the electric field strength in the QW on the applied voltage. [ABSTRACT FROM AUTHOR]

We investigate the quantification of entanglement between the photonic and excitonic modes in a semiconductor microcavity injected with squeezed light. By deriving and subsequently establishing the solutions to the quantum Langevin equations, we quantify the transient entanglement and the steady-state entanglement between the photonic and excitonic modes in the low-excitation regime. It turns out that the cavity mode and the exciton mode are entangled in both the weak and strong coupling regimes, and there is the entanglement between the cavity mode and the exciton mode even in the absence of direct coupling between them. Furthermore, though the transit entanglement increases with the squeeze parameter, it decreases with the initial average intensity of the cavity mode. Also, we demonstrate that, in the strong coupling regime, the steady-state entanglement grows with coupling strength while, in the weak coupling regime, it decreases. [ABSTRACT FROM AUTHOR]

Low dimensional perovskite forms multiple quantum wells (MQWs) structures that can be an efficient structure for light‐emitting diodes (LEDs). Here the use of different barrier molecules is demonstrated to create Ruddlesden–Popper and Dion–Jacobson 2D perovskite and implement them in LEDs. It is found that the aromatic barrier molecules are better performing in Perovskite LED (PeLED) compared to linear barrier molecules. The benzylammonium (BnzA), n = 5, shows the highest external quantum efficiency (EQE) of 16.65% compared to the di‐ammonium and the linear barrier molecules. The BnzA forms n = 1 inside the 3D perovskite, which provides a non‐radiative energy transfer from the wider bandgap, n = 1 perovskite, to the smaller bandgap, 3D perovskite, that presents radiative recombination. Optical characterizations support the MQW structure whereas physical characterizations show unique morphology of separate nanocrystals laying on top of thin perovskite film during the n = 5 BnzA crystallization. In addition, it is revealed that the barrier molecule type, in this case, the BnzA, is responsible for the formation of the MQW structure whereas other barrier molecules didn't show this structure. The formation of an additional low n‐value phase inside the 3D perovskite is beneficial for the enhancement of the radiative recombination which results in high EQE. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) layered materials provide an ideal platform for visualizing several quantum mechanical phenomena, such as quantum confinement, within a sheet of materials. In contrast to the case of quantum wells (QWs) realized through conventional semiconductor heterostructures, the QW made with 2D semiconductors offers a unique platform to explore many-body effects with its optical excitation and emission characteristics. Herein, we delve into the effect on the photoluminescence (PL) emission spectrum from chemical vapor deposition-grown monolayer (1L)-WS2 flakes upon being encapsulated by ultrathin ZnO films. We assemble a sandwich-type structure with 1L-WS2 using ZnO, a higher band gap semiconductor, and investigate the modulation of the PL emission from the WS2 flakes of subnanometer thickness resulting from the quantum confinement and doping effect. We have adopted excitation power- and temperature-dependent micro-PL spectral analysis to comprehend the contributions of neutral excitons, trions, biexcitons, and defects in the tunable PL from the sandwich structure. The PL of 1L-WS2 is partly influenced by strain and doping. Raman spectroscopy is utilized to understand the strain and doping effects induced by the ZnO layer on 1L-WS2. Unlike a typical quantum-well case, here, ZnO being a higher band gap semiconductor injects carriers onto the 1L-WS2, which, along with escalating the exciton density, causes the formation of multibody quasiparticles, such as trions and biexcitons. Cryogenic temperatures and high laser powers favor biexciton emission in monolayer WS2, restricting the QW-induced excitonic PL enhancement only to low excitation powers. This work offers insights into comprehension of the carrier dynamics in monolayer transition-metal dichalcogenides by encapsulation with ultrathin semiconductor layers and the modulation of its PL emission for applications in excitonic light emission. [ABSTRACT FROM AUTHOR]

In this paper, an n-i-p-type GaN barrier for the final quantum well, which is closest to the p-type GaN cap layer, is proposed for nitride light-emitting diodes (LEDs) to enhance the confinement of electrons and to improve the efficiency of hole injection. The performances of GaN-based LEDs with a traditional GaN barrier and with our proposed n-i-p GaN barrier were simulated and analyzed in detail. It was observed that, with our newly designed n-i-p GaN barrier, the performances of the LEDs were improved, including a higher light output power, a lower threshold voltage, and a stronger electroluminescence emission intensity. The light output power can be remarkably boosted by 105% at an injection current density of 100 A/cm2 in comparison with a traditional LED. These improvements originated from the proposed n-i-p GaN barrier, which induces a strong reverse electrostatic field in the n-i-p GaN barrier. This field not only enhances the confinement of electrons but also improves the efficiency of hole injection. [ABSTRACT FROM AUTHOR]

Generating a nonequilibrium spin polarization with a driving force is first realized by the electric current in a system with broken inversion symmetry and extended to that induced by the thermal current and that appearing in an inversionsymmetric system with locally broken inversion symmetry. This article theoretically explores the spin polarization generated by the thermal current and the locally broken inversion symmetry in a symmetric double-quantum well structure (DQWS). This thermally induced spin polarization (TISP) appears in the antiparallel configuration with the TISP of two wells in opposite directions. The calculation using the Boltzmann equation in the relaxation-time approximation under the condition of zero charge current shows that the local TISP exhibits the maximum at a finite Rashba spin-orbit interaction when the electron density is fixed. This is because the local TISP in the DQWS is enhanced at the chemical potential near the bottom of the first-excited sub-band. This enhancement also occurs in a single quantum well with globally broken inversion symmetry. Another finding is that the maximum of the local TISP appears at a nonzero interwell coupling. The spin current by the diffusion of the local TISP into an adjacent electrode is also calculated. [ABSTRACT FROM AUTHOR]

In this work, the influence of two-dimensional state density on oscillations of transverse electrical conductivity in heterostructures with rectangular quantum wells is investigated. A new analytical expression is derived for calculating the temperature dependence of the transverse electrical conductivity oscillation and the magnetoresistance of a quantum well. For the first time, a mechanism is developed for oscillating the transverse electrical conductivity and magnetoresistance of a quantum well from the first-order derivative of the magnetic field (differential) ∂ ρ ⊥ 2 d (E , B , T , d) ∂ B at low temperatures and weak magnetic fields. The oscillations of electrical conductivity and magnetoresistance of a narrow-band quantum well with a non-parabolic dispersion law are investigated. The proposed theory investigates the results of experiments of a narrow-band quantum well (InxGa1−xSb). The experiment shows that the oscillations of the transverse magnetoresistance of the InxGa1−xSb quantum filament, measured at a temperature of 2 K, transform into a continuous energy spectrum due to thermal washing under the influence of the temperature growth dynamics. [ABSTRACT FROM AUTHOR]

The features of one-dimensional vacuum tunneling and calculation of the tunneling current in barrier quantum structures with one and two wells are considered. The structures are formed by several electrodes: the cathode, the anode and two grids. The potential profiles are constructed by the method of multiple images. Equations for eigenvalues and metastable levels of a structure with an arbitrary potential profile are found. For full resonant tunneling, the metastable levels must fall into the region of the electron kinetic energy distribution at the cathode, which occurs in single-well structures in the absence of an anode voltage or at a low anode voltage compared to the voltage on the grids. A significant voltage at the anode leads to an asymmetric structure and incomplete resonant tunneling. In this case, a two-well structure with a double grid allows obtaining full resonant tunneling for a number of energies and increasing the tunneling current by orders of magnitude. [ABSTRACT FROM AUTHOR]

Weak localization in a highly disordered quantum well CdxHg1 – xTe/HgTe/CdxHg1 – xTe with a thickness of d = 20 nm is experimentally investigated. An analysis is made of the anomalous positive magnetoresistance (APM) caused by the suppression of the interference correction to the conductivity by a magnetic field on both sides of the charge neutrality point: for a two-dimensional semimetal and for a two-dimensional electronic metal. For the same values of resistivity, the APM peak in a 2D semimetal has a much wider width than in a 2D electron gas. A quantitative comparison of the obtained results with the theory allows, in particular, to conclude that the intensity of carrier transitions between subsystems in the 2D semimetal binary system is maximum near the charge neutrality point, where the concentrations of electrons and holes are close, and decreases as the difference in concentrations increases. [ABSTRACT FROM AUTHOR]

Recent advancements in terahertz (THz) wave technology have highlighted the criticality of circular-polarization detection, fostering the development of more compact, efficient on-chip THz circular-polarization detectors. In response to this technological imperative, we presented a chiral-antenna-integrated GaAs/AlGaAs quantum well (QW) THz detector. The chiral antenna selectively couples the incident light of a specific circular-polarization state into a surface-plasmon polariton wave that enhances the absorptance of the QWs by a factor of 12 relative to a standard 45° faceted device, and reflects a significant amount of the incident light of the orthogonal circular-polarization state. The circular-polarization selectivity is further enhanced by the QWs with a strong intrinsic anisotropy, resulting in a circular-polarization extinction ratio (CPER) as high as 26 at 6.52 THz. In addition, the operation band of the device can be adjusted by tuning the structural parameters of the chiral structure. Moreover, the device preserves a high performance for oblique incidence within a range of ±5°, and the device architecture is compatible with a focal plane array. This report communicates a promising approach for the development of miniaturized on-chip THz circular-polarization detectors. [ABSTRACT FROM AUTHOR]

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In this work, the dependence of the oscillation of the combined density of states on a strong magnetic field in heterostructures based on a rectangular quantum well is studied. The effect of a quantizing magnetic field on the temperature dependence of the combined density of states in nanoscale straight-band heterostructures is investigated. A new mathematical model has been developed for calculating the temperature dependence of the two-dimensional combined density of quantum well states in quantizing magnetic fields. The proposed model explains the experimental results in nanoscale straight-band semiconductors with a parabolic dispersion law. [ABSTRACT FROM AUTHOR]

In this work, the influence of light on the temperature dependence of transverse magnetoresistance oscillations is studied. A generalized mathematical expression that calculates the temperature and light dependence of the quasi-Fermi levels of small-scale p-type semiconductor structures in a quantizing magnetic field is derived. New analytical expressions have been found to represent the temperature dependence of transverse differential magnetoresistance oscillations in dark and light situations, taking into account the effect of light on the oscillations of the Fermi energy of small-scale semiconductor structures. A mathematical model has been developed that determines the light dependence of the second-order derivative of the transverse magnetoresistance oscillations of p-type semiconductors with quantum wells by magnetic field induction. A new theory is proposed, which explains the reasons for the significant shift of the differential magnetoresistance oscillations along the vertical axis measured in the experiment for dark and light conditions. [ABSTRACT FROM AUTHOR]

A systematic study of a series of InGaAs/GaAs lasers in the 1–1.3 μm optical range based on quantum wells (2D), quantum dots (0D), and quantum well-dots of transitional (0D/2D) dimensionality is presented. In a wide range of pump currents, the dependences of the lasing wavelength on the layer gain constant, a parameter which allows comparing lasers with different types of active region and various waveguide designs, are measured and analyzed. It is shown that the maximum optical gain of the quantum well-dots is significantly higher, and the range of lasing rawavelengths achievable in edge-emitting lasers without external resonators is wider than in lasers based on quantum wells and quantum dots. [ABSTRACT FROM AUTHOR]

A comparative study of the circular polarization degree dependences on external magnetic field was carried out in spin light-emitting diodes including semiconductor InGaAs/GaAs heterostructure and a magnetic CoPt contact and in control non-magnetic structures with an Au contact. In a weak magnetic field, the magnetic field dependence of electroluminescence circular polarization degree is similar to the magnetic field dependence of magnetization: it represents a hysteresis loop with saturation in a field of ~0.3 T. In a strong magnetic field, an additional linear contribution to the circular polarization degree is detected. This contribution is associated with the Zeeman splitting of energy levels. The magnitude of the linear contribution depends on the position of the quantum well relative to the ferromagnet/semiconductor interface. The obtained dependence is associated with the influence of the magnetic field of the inhomogeneously magnetized CoPt electrode on the spin relaxation time of carriers. [ABSTRACT FROM AUTHOR]

We report the fabrication of 1.5–1.6 μm light-emitting modules based on an AlGaInAs/InP heterostructure with strain-compensated quantum wells in new, smaller, thermally stabilized housings. Their performance is tested under extreme operating conditions. The reliability of such modules and stability under the influence of climatic factors is studied. [ABSTRACT FROM AUTHOR]

We have demonstrated a quantum cascade laser (QCL) with a generation frequency of about 3.8 THz, grown by metal-organic vapor phase epitaxy. The multilayer heterostructure for QCLs consists of 185 repetitions of an active module containing four GaAs/Al0.15Ga0.85As quantum wells. The threshold current and threshold voltage of the fabricated QCL were 2.25 kA/cm2 and 19.7 V, respectively. The QCL oscillations were carried out in the multimode regime, and the detection of terahertz radiation continued with an increase in the laser temperature up to 60 K. [ABSTRACT FROM AUTHOR]

In this paper we develop a stochastic simulation algorithm for electron transport in a DA-pHEMT heterostructure. Mathematical formulation of the problem of electron gas transport in the heterostructure in the form of a coupled system of Poisson, Schrödinger and kinetic Boltzmann equations is given. A Monte Carlo model of electron transport in DA-pHEMT heterostructures which accounts for multivalley parabolic band structure, as well as relevant formulas for calculating electron scattering rates and scattering phase functions on polar optical, intervalley phonons and on impurities are developed. The results of a computational experiment involving the solution of the system of Poisson–Schrödinger–Boltzmann equations for the AlGaAs/GaAs/InGaAs/GaAs/AlGaAs heterostructure are presented. The distribution of electrons by energy subband in the main and satellite valleys and the field dependences of the electron drift velocity in each valley are calculated. It was discovered that there is no spatial transfer of electrons into wide-gap AlGaAs layers due to high barriers created by modulated-doped impurities. A comparative analysis of the electron drift velocities in the studied DA-pHEMT heterostructures and in the unstrained layer of the InGaAs is given. [ABSTRACT FROM AUTHOR]

In this study, we investigated, for the first time, the effects of the spatially varying effective mass, asymmetry parameter, and well width on the electronic and optical properties of a quantum well which has an improved Rosen–Morse potential. Calculations were made within the framework of the effective mass and parabolic band approximations. We have used the diagonalization method by choosing a wave function based on the trigonometric orthonormal functions to find eigenvalues and eigenfunctions of the electron confined within the improved Rosen–Morse potential. Our results show that the position dependence mass, asymmetry, and confinement parameters cause significant changes in the electronic and optical properties of the structure we focus on since these effects create a significant increase in electron energies and a blue shift in the absorption spectrum. The increase in energy levels enables the development of optoelectronic devices that can operate at wider wavelengths and absorb higher-energy photons. Through an appropriate choice of parameters, the Rosen–Morse potential offers, among many advantages, the possibility of simulating heterostructures close to surfaces exposed to air or vacuum, thus giving the possibility of substantially enriching the allowed optical transitions given the breaking of the system´s symmetries. Similarly, the one-dimensional Rosen–Morse potential model proposed here can be extended to one- and zero-dimensional structures such as core/shell quantum well wires and quantum dots. This offers potential advancements in fields such as optical communication, imaging technology, and solar cells. [ABSTRACT FROM AUTHOR]

The photovoltaic conversion efficiency of a single-intermediate band solar cell that incorporates a double quantum well structure consisting of GaAs/InAs/GaAs/InAs/GaAs embedded in the intrinsic region of conventional p-i-n structure is analyzed. The width of the intermediate band and the solutions for the two lowest energy states has been determined by solving the two-impurities-related Schrodinger equation based on the Numerov method. The position of these impurities determines three distinct cases: the system in the absence of impurities (Case 1), impurities at the center of GaAs quantum barriers (Case 2), and impurities at the center of InAs quantum wells (Case 3). The photovoltaic conversion efficiency has been calculated as a function of the widths L y H of the quantum well structures. The obtained results indicate an improvement in efficiency under the specific conditions of these parameters. [ABSTRACT FROM AUTHOR]

We demonstrate a fourth-order Vernier serious-coupled microring resonator (MRR) filter based on the InGaAs/InAlAs five-layer asymmetric coupled quantum-well (FACQW) waveguide. As the tuning of the main resonance wavelength is driven by the electrorefractive index change in the FACQW layer caused by the quantum-confined Stark effect (QCSE), the MRR filter has lower tuning power consumption and high-speed operation. The free spectral range (FSR) of the MRR filter is extended to 9.4 nm. The main resonant peak is discretely tuned within one FSR, leading to an increase in the wavelength channel. [ABSTRACT FROM AUTHOR]

The influence of InGaAlAs waveguide composition on the photoluminescence and electroluminescence of 1550 nm spectral range heterostructures based on thin strained In0.74Ga0.26As quantum wells has been studied. An approach is proposed that allows based on the analysis of electroluminescence to carry out a comparative analysis of the deferential gain in fabricated laser diodes. It is shown that decrease of the molar fraction of aluminum in waveguide InGaAlAs layers matched in lattice constant with InP leads to falling of integrated photoluminescence intensity, however, laser diodes with In0.53Ga0.31Al0.16As waveguide layers demonstrate a higher differential gain compared to laser diodes with In0.53Ga0.27Al0.20As waveguide. [ABSTRACT FROM AUTHOR]

In this current study, we theoretically study how anisotropic parabolic potential affects polaron n excited state in strongly coupled polar crystals (KBr, KCl, RbCl) in asymmetric Gaussian potential quantum wells, through the combined approach of one unitary transformation and linear combination operator. In the restriction limit of strong coupling, we derive rigorous results for excited state energy. By using this combination method, polaron energy and electron energy are compared which energy both polaron and electron is affected by confined potential. In addition, the relationship between energy difference and coupling strength is also discussed. It is hoped that the theoretical results reveal a promising and importance of further study of polaron. [ABSTRACT FROM AUTHOR]

The results of studying the effect of neutron irradiation on the spectral characteristics of InxGa1 –xN LEDs are presented. The mechanism responsible for the shift of the maximum of the LED emission spectra under the influence of neutrons is determined. Coherence is shown between the radiation sensitivity of the spectral characteristics of the sample active layers and the composition of the InxGa1 –xN solid solution. An analytical calculation is carried out to estimate the possible maximum shift of the luminescence spectrum of InxGa1 –xN LEDs after neutron exposure. [ABSTRACT FROM AUTHOR]

In this work, we report on the efficiency of single InGaN/GaN quantum wells (QWs) grown on thin (<1 µm) GaN buffer layers on silicon (111) substrates exhibiting very high threading dislocation (TD) densities. Despite this high defect density, we show that QW emission efficiency significantly increases upon the insertion of an In-containing underlayer, whose role is to prevent the introduction of point defects during the growth of InGaN QWs. Hence, we demonstrate that point defects play a key role in limiting InGaN QW efficiency, even in samples where their density (2–3 × 10 9 cm − 2 ) is much lower than that of TD (2–3 × 10 10 cm − 2 ). Time-resolved photoluminescence and cathodoluminescence studies confirm the prevalence of point defects over TDs in QW efficiency. Interestingly, TD terminations lead to the formation of independent domains for carriers, thanks to V-pits and step bunching phenomena. [ABSTRACT FROM AUTHOR]

We theoretically investigate the spatial-non-homogeneous laser pulse propagation through the quantum well. It is shown that the odd-order and even-order harmonic generations can be found due to breaking the inversion symmetry of the system. Importantly, the spectral intensity of high-order harmonics can be enhanced by changing the propagation distances and spatial-non-homogeneity of incident laser field. Moreover, the quantum well's shape has an important influence on the peak intensities of high-order harmonic generations, which may provide a new way to improve the spectral intensity of high-order harmonic generations. [ABSTRACT FROM AUTHOR]

In this work, we conduct research of spectral and power characteristics of quantum cascade lasers (QCLs) based on a GaAs/Al0.15Ga0.85As active region emitting at 2.3 (A), 3.2 (B) and 4.1 (C) THz. The QCL devices had a double-metal Au waveguide and operated in pulsed mode with 1.5–9 μs pulses at 20 Hz repetition rate. Using the integral output power curves measured with different pulse durations, we consider the potential mechanisms of QCL temperature degradation using Arrhenius plots. Moreover, we present the spectra of the lasers measured at fixed operating points for devices A, C and with current scanning for device B in a wide temperature range from 5 to 120 K. We hope that our results will prove useful for research concerning QCL maximum operating temperatures. [ABSTRACT FROM AUTHOR]

We employed the selective-area-epitaxy technique using metalorganic chemical vapor deposition to fabricate and study samples of semiconductor heterostructures that incorporate highly strained InGaAs quantum wells (980–990 nm emission wavelength). Selective area epitaxy of InGaAs quantum wells was performed on templates that had a patterned periodic structure consisting of a window (where epitaxial growth occurred) and a passive mask (where epitaxial growth was suppressed), each with a width of 100 µm for every element. Additionally, a selectively grown potential barrier layer was included, which was characterized by an almost parabolic curvature profile of the surface. We conducted a study on the influence of the curvature profile of the growth surface on the optical properties of InGaAs quantum wells and the spatial distribution of composition in an ultrawide window. Our results showed that, under fixed selective-area-epitaxy conditions, the composition of the InxGa1−xAs and the wavelength of the quantum-well emission changed across the width of the window. Our study demonstrates that increasing the curvature profile of the growth surface of highly strained quantum wells leads to a transition in the photoluminescence wavelength distribution profile across the window, from quasi-parabolic to inverted parabolic. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the mobility μ and thermopower S of a quasi-two-dimensional hole gas (Q2DHG) confined in a Si/Si1-xGex/Si finite square quantum well (QW) due to different scattering mechanisms such as alloy disorder (AD), surface roughness (SR), misfit deformation potential (DP), piezoelectric charge (PE), remote impurity (RI), acoustic phonon (ac) via deformation potential (acDP) and piezoelectric fields (acPE). We use the screened theory in the calculation of the mobility due to all considered scattering mechanisms and investigate the dependence of screening effects on QW height. We show that the infinite model underestimates the surface roughness-, acoustic phonon-limited and total mobility of narrow QWs especially at high temperatures T. We find that, for system parameters considered, Sd (Sg) decreases slightly (increases notably) with increasing barrier height, and at low hole densities the overall thermopower is determined mainly by Sd and its dependence on barrier height is very weak. Our results also indicate that, in the case of narrow QWs, the infinite model overestimates the total thermopower and the screening reduces remarkably both Sg and Sd particularly in the range of high T. [ABSTRACT FROM AUTHOR]

Low-dimensional semiconductor systems have attracted considerable attention of the researchers because of their applications such as speed circuits, optical devices etc. The application of external perturbations like magnetic field can change the properties of these systems. Study on tilted magnetic fields is of interest theoretically as it illustrates special confinement effects. In the present study, we calculate the binding energy of a hydrogenic donor in a quantum well with a potential profile proportional to |z|2/3, called Near Triangular Quantum Well (NTQW), in the presence of a magnetic field tilted by an angle θ with the growth axis, using variational method. Calculations of hydrogenic donor binding energies are made by varying the well width (L), Aluminium composition (x), strength of the magnetic field (γ) and the tilt angle (θ). Integrated probability density (P) of finding a hydrogenic donor in NTQW is also analysed as a function of well width (L). [ABSTRACT FROM AUTHOR]

Regardless of the fact that the confirmed Power Conversion Efficiency (PCE) of kesterite materials for photovoltaic cells is lower than that of other chalcogenide materials, there is still sign of improvement due to their high absorption rate, flexibility to have a tunable bandgap, abundance in nature, and so on.The primary objectives of this study was to assess the combined utilisation of quantum dots and quantum wells in kesterite material. This was achieved through three key approaches: firstly, by altering the quantity of quantum dots and wells present in the nanostructure; secondly, by modifying the composition of the dots and well material through adjustments in the Sulphur and Selenium ratio of CZTSSe. The third aspect to consider is the analysis of the effect of changes in operating temperature on high-performing nanostructures, building upon the information gathered from the previous two processes. Electrical properties such as PCE, $ V_{oc}$ , $ J_{sc}$ , and IV curve have been analyzed so that the performance of the hybrid structure can be examined. A quantum well and a quantum dot layer are both present in the p-i-n structure. The quantum dot layer is composed of ten quantum dots placed in an array. The effects of quantum dot thickness (5 and 10 nm) were also investigated. According to the findings, as few as three quantum dot layers and three quantum wells resulted in a 21% PCE. By varying the operating temperature between 250 K to 500 K, the temperature dependency of high-PCE structures was examined. [ABSTRACT FROM AUTHOR]

It is well known that the laser diode performance will inevitably deteriorate when the device is heated. It has been a difficult issue to solve to date. In this letter, we are reporting a new solution to improve high-temperature performance of the laser diodes. The device uses a kind of directly-coupled well-wire hybrid quantum confinement (HQC) structure of the active medium based on the InGaAs–GaAs–GaAsP material system. This special HQC structure is constructed based on the strain-driven indium (In)-segregation effect and the growth orientation-dependent on-GaAs multi-atomic step effect. The measurement and analysis for the HQC laser sample show that the carrier leakage loss, the Auger recombination and gain-peak shifting due to heating are reduced in the HQC structure. It therefore increases the optical gain for lasing at high temperature. The power conversion efficiency is enhanced by >57% and the threshold carrier density drops by >24% at T ⩾ 360 K, in comparison to the traditional quantum-well laser performance. A higher characteristic temperature of 240 K is obtained as well. It implies the better thermal stability of the HQC laser structure. These achievements show a significant prospect for developing high thermo-optic performance of laser diodes. [ABSTRACT FROM AUTHOR]

This paper provides a theoretical investigation of the ground and first excited-states donor impurity binding energy and the linear and nonlinear optical absorption coefficients in quantum well with novel modulated potential called Redouane-Haddou potential (RHP). Within the effective-mass theory, the Schrödinger equation has been calculated numerically using the finite element method. The analytical expressions of the optical absorption coefficients are obtained within compact density matrix theory. Our results reveal that the A-parameter has a significant influence on the confinement profile and electron states, therefore, the binding energy as well as the optical properties of the investigated system. It increases the binding energy and redshift (blueshift) associated with drop (improve) of the linear and nonlinear optical absorption coefficients related to 2p→1s, 2p→2s, and 3s→2p transitions. Moreover, it is noticed that with an appropriate choice of the A-parameter and structure dimension, the optical response of the investigated system can be tailored in a controllable manner. [ABSTRACT FROM AUTHOR]

The recombination dynamics are studied in viscous electron–hole plasma, consisting of electrons and photo-generated heavy and light holes, formed in the high-mobility mesoscopic GaAs channel. It is shown that an increase in the pump power reduces the concentration and mobility of background electrons, which, in turn, slows down their recombination with photogenerated holes. At a critical pump power, the recombination time begins to decrease, which is a consequence of the transition of a viscous electron–hole plasma from the hydrodynamic regime to the Drude diffusive regime. The observed transition occurs when the scattering of electrons with disorder begins to dominate over electron–electron scattering, which leads to the transformation of an inhomogeneous Poiseuille charge flow into a homogeneous diffusion flow. As a result, an optical analogue of the Gurzhi effect has been found. [ABSTRACT FROM AUTHOR]

Theoretical analysis of the effect of quantum well thickness on the energy band dispersion curve, matrix elements, transition energy, optical gain, and transition wavelength of the type-II In0.7Ga0.3As/GaAs0.4Sb0.6 heterostructure based on InP substrate using six bands k.p method has been done. A decrease in the optical gain and an increase in the transition wavelength are reported with an increase in the quantum well thickness. The transition wavelength is located in the short wavelength infrared region (SWIR). An increase in optical gain is observed with an increase in the injected carrier density. In conclusion, the results clarified that In0.7Ga0.3As/GaAs0.4Sb0.6 based heterostructures are suitable for making optoelectronic devices in the SWIR region. [ABSTRACT FROM AUTHOR]