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Understanding quantum systems is of significant importance for assessing the performance of quantum hardware and software, as well as exploring quantum control and quantum sensing. An efficient representation of quantum states enables realizing quantum state tomography with minimal measurements. In this study, we propose an alternative approach to state tomography that uses tensor network representations of mixed states through locally purified density operators and employs a classical data postprocessing algorithm requiring only local measurements. Through numerical simulations of one-dimensional pure and mixed states and two-dimensional pure states up to size 8 × 8, we demonstrate the efficiency, accuracy, and robustness of our proposed methods. Experiments on the IBM and Quafu Quantum platforms complement these numerical simulations. Our study opens avenues in quantum state tomography for two-dimensional systems using tensor network formalism. Quantum state tomography is a fundamental tool for assessing the performance of quantum hardware and plays a crucial role in advancing quantum information processing. The authors present a method based on tensor network representations and local measurements, demonstrating accuracy and efficiency in characterizing noisy quantum states. [ABSTRACT FROM AUTHOR]

The construction of miniaturized light-emitting diodes (LEDs) with high external quantum efficiency (EQE) at room temperature remains a challenge for on-chip optoelectronics. Here, we demonstrate microsized LEDs fabricated by a dry-transfer van der Waals (vdW) integration method using typical layered Ruddlesden-Popper perovskites (RPPs). A single-crystalline layered RPP nanoflake is used as the active layer and sandwiched between two few-layer graphene contacts, forming van der Waals LEDs (vdWLEDs). Strong electroluminescence (EL) emission with a low turn-on current density of ~20 pA μm-2 and high EQE exceeding 10% is observed at room temperature, which sets the benchmark for the EQE of vdWLEDs ever recorded. Such efficient EL emission is attributed to the inherent multiple quantum well structure and high photoluminescence quantum yield (~35%) of RPPs and a low charge injection barrier of ~0.10 eV facilitated by the Fowler-Nordheim tunneling mechanism. These findings promise a scalable pathway for accessing high-performance miniaturized light sources for on-chip optical optoelectronics. [ABSTRACT FROM AUTHOR]

In our quest to understand the generation of cosmological perturbations, we face two serious obstacles: we do not have direct information about the environment experienced by primordial perturbations during inflation, and our observables are practically limited to correlators of massless fields, heavier fields and derivatives decaying exponentially in the number of e-foldings. The flexible and general framework of open systems has been developed precisely to face similar challenges. Building on previous work, we develop a Schwinger-Keldysh path integral description for an open effective field theory of inflation, describing the possibly dissipative and non-unitary evolution of the Goldstone boson of time translations interacting with an unspecified environment, under the key assumption of locality in space and time. Working in the decoupling limit, we study the linear and interacting theory in de Sitter and derive predictions for the power spectrum and bispectrum that depend on a finite number of effective couplings organised in a derivative expansion. The smoking gun of interactions with the environment is an enhanced but finite bispectrum close to the folded kinematical limit. We demonstrate the generality of our approach by matching our open effective theory to an explicit model. Our construction provides a standard model to simultaneously study phenomenological predictions as well as quantum information aspects of the inflationary dynamics. [ABSTRACT FROM AUTHOR]

Red micro-light-emitting diodes (μ-LEDs) with AlGaInP/GaInP multiple quantum wells are fabricated with an oxide perimeter region to control the current injection path. When the values of the external quantum efficiency (EQE) of the 30 μm-size μ-LED with the oxide perimeter region are compared with those of the device without the oxide perimeter region, an improvement as high as 40% is observed at current densities <80 A/cm2. From the finite-difference time-domain simulation of the light-extraction efficiency (LEE), which shows that the LEE of the device with the oxide perimeter region is ∼12% smaller than that of the device without the oxide perimeter region, it can be seen that the increased EQE is attributed to the improvement of the internal quantum efficiency (IQE). Since the oxide perimeter region limits the current paths to the sidewalls of the μ-LED chips, the nonradiative recombination via sidewall defects is considered suppressed, resulting in the improvement of the IQE. The oxidation of the AlGaAs layer utilized in this work is easy to implement and accurately controllable, suitable for mass-production of high-efficiency red μ-LEDs for display applications. [ABSTRACT FROM AUTHOR]

Spherical quantum wells (SQWs) have proven to be excellent materials for suppressing Auger recombination due to their expanded confinement volume. However, research on the factors and mechanisms of their high-intensity optical properties, such as multiexciton properties and third-order optical nonlinearities, remains incomplete, limiting further optimization of these properties. Here, a series of CdS/CdSe (xML)/CdS SQWs with varying CdSe layer thicknesses were prepared. The modulation effects of CdSe shell variations on the PL properties, defect distribution, biexciton binding energy, and third-order optical nonlinearities of the SQWs were investigated, and their impact on the material's multiexciton properties was further analyzed. Results showed that the typical CdS/CdSe(3ML)/CdS sample exhibited a large volume-normalized two-photon absorption cross-section (18.17 × 102 GM/nm3) and favorable biexciton characteristics. Optical amplification was observed at 12.4 μJ/cm2 and 1.02 mJ/cm2 under one-photon (400 nm) and two-photon (800 nm) excitation, respectively. Furthermore, different amplified spontaneous emission spectra were observed for the first time under one/two-photon excitation. This phenomenon was attributed to thermal effects overcoming the biexciton binding energy. This study provides valuable insights for further optimizing multiexciton gain characteristics in SQWs and developing optical gain applications. [ABSTRACT FROM AUTHOR]

This paper reports on a monolithically integrated gallium arsenide (GaAs)-based photonic integrated circuit platform for wavelengths around 1064 nm. Enabled by spatially selective quantum well removal and two-step epitaxial growth, it supports on-chip gain as well as passive waveguides. In addition, shallow- and deep-etched waveguides are realized. The former result in waveguide losses of less than 2 dB/cm, while the latter enable compact integrated waveguide components. To demonstrate the performance of the platform, racetrack ring resonators based on deep-etched Euler bends and shallow-etched directional couplers are realized, achieving high intrinsic quality factors of 2.6 × 105 and 3.2 × 105 for the fundamental TE and TM mode, respectively. To demonstrate the use of these resonators, ring-resonator-coupled lasers are fabricated, resulting in one-sided output powers of up to 14 mW and single-mode operation with 40 dB side-mode suppression. The successful integration of ring resonators on a GaAs-based active/passive photonic integrated circuit platform paves the way for the realization of fully monolithic, widely tunable, and narrow linewidth ring-resonator-coupled laser sources. [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]

The impact of delta-doping modulation and electric field influence within a nanostructure consisting of three GaAs quantum wells (QWs) separated by AlGaAs barriers was investigated. The quantized energy levels, Fermi energy, wavefunctions, self-consistent potential, and electron density distribution were evaluated by a self-consistent solution of the Schrödinger and Poisson equations using the finite element method within the FEniCS project in Python. The results indicate that increasing the electric field reduces energy levels and Fermi energy. In addition, the delta-doping position and electric field significantly affect the self-consistent potential and electron density distribution. This study provides a possibility to tailor optical properties, such as the linear absorption coefficient and photoluminescence, by adjusting geometrical and non-geometrical parameters, including donor density, enhancing the functionality of doped QWs in designing high electron mobility transistors. [ABSTRACT FROM AUTHOR]

A type I InAs(Sb)/InAsPSb strain engineered multiple quantum wells light emitting diodes system has been demonstrated. Tensile InAsPSb quantum barriers with a high degree of band offset (∆EC = 116–123 meV, ∆EV = 193–250 meV) were used to compensate for the high compressive strain of the InAs(Sb) quantum wells. The structure was grown on the n+-InAsxP1−x metamorphic buffer with a high degree of relaxation (98%), low surface roughness (0.69 nm), and low dislocation density. Through careful strain engineering design, the compressive strain of InAs(Sb) reaches 0.57%–1.52% without strain relaxation. The incorporation of Sb into the multiple quantum wells not only reduces the bandgap but also improves the interface quality by acting as an effective surfactant. Structural analysis reveals superior quality in InAsSb/InAsPSb multiple quantum wells compared to InAs/InAsPSb multiple quantum wells, demonstrating significantly reduced interface roughness and suppression of the Stranski–Krastanov growth mode. Room temperature electroluminescence measurements show a tunable emission wavelength ranging from 2.7 to 3.3 μm, accompanied by a narrow full width at half maximum value of 45 meV. Photoluminescence analysis indicates that the internal quantum efficiency of InAsSb/InAsPSb multiple quantum wells is 5.5%, which is 7 times higher than that of InAs/InAsPSb. [ABSTRACT FROM AUTHOR]

The optical properties of wurtzite violet InGaN/GaN coupled quantum well (QW) structures are experimentally studied using photoluminescence (PL) and electroluminescence (EL) spectroscopy. Two emission peaks, referred to as Peak H and Peak L, are observed in both PL and EL spectra, due to the ground state splitting induced by the well coupling. Experimental PL and EL results reveal that coupled QWs show different optical responses due to the different variation in the electric field inside the QW structure. Since the direction of the polarization electric field of the as-grown well/barrier layers is different, the external electric field applied by electrodes can change the energy band alignment between the well and the barrier layers, thus adjusting the coupling between the wells. Our results provide relevant information to improve our understanding of the optical properties of InGaN/GaN QWs and to develop novel optoelectronic devices. [ABSTRACT FROM AUTHOR]

This work reports on the possibility of sustaining a stable operation of polarization-doped InGaN light emitters over a particularly broad temperature range. We obtained efficient emission from InGaN light-emitting diodes between 20 K and 295 K and from laser diodes between 77 K and 295 K under continuous wave operation. The main part of the p-type layers was fabricated from composition-graded AlGaN. To optimize injection efficiency and improve contact resistance, we introduced thin Mg-doped layers of GaN (subcontact) and AlGaN (electron blocking layer in the case of laser diodes). In the case of LEDs, the optical emission efficiency at low temperatures seems to be limited by electron overshooting through the quantum wells. For laser diodes, a limiting factor is the freeze-out of the magnesium-doped electron blocking layer for temperatures below 160 K. The GaN:Mg subcontact layer works satisfyingly even at the lowest operating temperature (20 K). [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]

This work presents an analysis and design of the two barrier-quantum well asymmetric spacer tunnel layer (QW-ASPAT) diodes for implantable rectenna circuits application. The RF and DC characteristic of a 10×10 μm² QW-ASPAT devices based on GaAs and In0.53Ga0.47As platform was simulated and extracted by using SILVACO atlas software. The highest extracted curvature coefficient, kv value of the both QW-ASPAT devices at zero bias was about 33V-1 compared with the standard structure GaAs/InGaAs was about 13V-1. The effects of changing in the thickness of the thin AlAs-barrier, the well width, and the spacer layer are fully investigated on the non-linear relationship between current and voltage of these diodes. A CV simulation was carried out, and it was found that the addition of the quantum-well layer between spacers and barrier reduced the junction capacitance of the QW-ASPAT device when compared with standard devices. The cut-off frequency of the proposed QW-GaAs and QW-InGaAs devices are 26GHz and 46GHz respectively. Finally, we conclude that the QW-ASPAT device is the best structure and can be used for microwave rectifiers in the miniaturized integrated rectenna systems. [ABSTRACT FROM AUTHOR]

This paper explores the optical limiting (OL) characteristics of an input probe field within a closed-loop asymmetric coupled quantum well (ACQW) system. Our research reveals that the application of Terahertz (THz) coupling laser fields can induce the OL behavior within the THz domain in the ACQW. The study demonstrates that revers saturable absorption arises through cross-Kerr nonlinearity, contributing to the emergence of OL behavior. Additionally, it is shown that the self-defocusing is induced concurrently within the system, further enhancing nonlinear refractive OL effects. Furthermore, it is revealed that the properties of induced OL can be manipulated by adjusting the characteristics of the applied fields. The discovered outcomes hold potential utility in safeguarding sensors and detectors operating within the THz band. [ABSTRACT FROM AUTHOR]

The Rashba effect of polaron in RbCl triangular quantum wells under the influence of a magnetic field is theoretically studied, and the expression of the ground state energy of the polaron is obtained within the Pekar variational method. The ground state energy of the polaron splits into two branches due to the Rashba effect. This phenomenon fully demonstrates that the influence of orbit and spin interaction in different directions on the energy of the polaron is not negligible. Because the contribution of the magnetic field cyclotron resonance frequency to the Rashba spin-orbit splitting is a positive value, the energy spacing becomes larger as the magnetic field cyclotron resonance frequency increases. Due to the spin-orbit coupling interaction, the energy splits at zero field. The total energy is reduced due to the presence of phonon. Therefore, the polaron state is more stable than the bare electron state, and the polaron energy splitting is more stable. [ABSTRACT FROM AUTHOR]

Quantum computing has emerged as a transformative paradigm, with revolutionary potential in numerous fields, including quantum image processing and compression. Applications that depend on large scale image data could benefit greatly from parallelism and quantum entanglement, which would allow images to be encoded and decoded with unprecedented efficiency and data reduction capability. This paper provides a comprehensive overview of the rapidly evolving field of quantum image compression, including its foundational principles, methods, challenges, and potential uses. The paper will also feature a thorough exploration of the fundamental concepts of quantum qubits as image pixels, quantum gates as image transformation tools, quantum image representation, as well as basic quantum compression operations. Our survey shows that work is still sparse on the practical implementation of quantum image compression algorithms on physical quantum computers. Thus, further research is needed in order to attain the full advantage and potential of quantum image compression algorithms on large-scale fault-tolerant quantum computers. [ABSTRACT FROM AUTHOR]

The aluminum gallium nitride (AlGaN)-based deep-ultraviolet light-emitting diode (DUV-LED) has been a prominent device due to its contribution in various fields. The electron blocking layer (EBL) is an additional layer in the epitaxy of the DUV-LED with the aim of reducing the overflow of electrons and improving the hole injection, consequently increasing the performance of the DUV-LED. However, the threshold of the EBL thickness and its influence on the electrical and optical properties is still not fully understood. Hence, the purpose of this research is to investigate the effects of varying the EBL thickness, ranging from 5 nm up to 60 nm, and investigate the threshold of EBL thickness for the AlGaN-based DUV-LED. The analysis includes the internal quantum efficiency (IQE), luminescence spectrum, band diagram behavior, and the current density of the carrier. It is found that EBL thickness of 15 nm produces the highest IQE (39.69%) for the DUV-LED with a single quantum well structure, where the wavelength emitted is ~ 257 nm, which is within the ultraviolet C (UVC) range. [ABSTRACT FROM AUTHOR]

This research explores a comprehensive examination of gate underlap incorporated strained channel Cylindrical Gate All Around Nanowire FET having enriched performances above the requirement of the 2 nm technology node of IRDS 2025. The device installs a combination of strain engineering based quantum well barrier system in the channel region with high-k spacers sandwiching the device underlaps and stack high-k gate-oxide. The underlaps are prone to parasitic resistance and various short channel effects (SCEs) hence, are sandwiched by HfO2 based high-k. This SCE degradations and a strong electric field in the drain-channel region is rendered controlling the leakages. The strain based Nanosystem engineering is incorporated with Type-II heterostructure band alignment inducing quantum well barrier mechanism in the ultra-thin cylindrical channel region creating an electrostatic charge centroid leading to energy band bending and splitting among the two-fold and four-fold valleys of the strained Silicon layer. This provides stupendous electron mobility instigating high current density and electron velocity in the channel. Thereby, the device is susceptible to on-current enhancement via ballistic transport of carriers and carrier confinement via succumbing of quantum charge carriers. The device transconductance, Ion, Ioff, Ion/Ioff ratio are measured and the output performance (ID-VDS) characteristics is determined providing emphatic enrichments in contrast to the existing gate all-around FETs as well as the 2 nm technology node data of IRDS 2025. Hence, the strained channel Nanowire FET device developed here is presented here as the device of the future for various digital applications, RF applications and faster switching speed. [ABSTRACT FROM AUTHOR]

Quasi‐2D perovskite quantum wells are increasingly recognized as promising candidates for direct‐conversion X‐ray detection. However, the fabrication of oriented and uniformly thick quasi‐2D perovskite films, crucial for effective high‐energy X‐ray detection, is hindered by the inherent challenges of preferential crystallization at the gas‐liquid interface, resulting in poor film quality. In addressing this limitation, a carbonyl array‐synergized crystallization (CSC) strategy is employed for the fabrication of thick films of a quasi‐2D Ruddlesden‐Popper (RP) phase perovskite, specifically PEA2MA4Pb5I16. The CSC strategy involves incorporating two forms of carbonyls in the perovskite precursor, generating large and dense intermediates. This design reduces the nucleation rate at the gas‐liquid interface, enhances the binding energies of Pb2+ at (202) and (111) planes, and passivates ion vacancy defects. Consequently, the construction of high‐quality thick films of PEA2MA4Pb5I16 RP perovskite quantum wells is achieved and characterized by vertical orientation and a pure well‐width distribution. The corresponding PEA2MA4Pb5I16 RP perovskite X‐ray detectors exhibit multi‐dimensional advantages in performance compared to previous approaches and commercially available a‐Se detectors. This CSC strategy promotes 2D perovskites as a candidate for next‐generation large‐area flat‐panel X‐ray detection systems. [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]

Two previously undescribed cationic indole alkaloids, named ophiorrhines L (1) and M (2), was isolated from the Ophiorrhiza japonica. The structures were elucidated based on spectroscopic data and quantum calculations as well as X-ray crystallographic analysis. Alkaloids 1 and 2 exhibited moderate inhibitory activities on XOD (Xanthine Oxidase) with IC50 values 42.5 and 22.6 μM, respectively. [ABSTRACT FROM AUTHOR]

In this study, we introduced a new nonlocal complex derivative operator in fractal dimension based concurrently on the concept of "nonlocal generalized complex backward-forward coordinates" and the "product-like fractal measure". The quantization of the theory in fractal dimension leads to a higher order Schrödinger equation characterized by a higher order energy operator. As an illustration, we have discussed the cases of infinite quantum well and power-law potentials. Their associated zero-point energies were found to depend on the numerical value of the fractal dimension. For the infinite well, the decrease in zero-point energy with fractal dimension may result in the emission of large wavelengths photons observed experimentally in X-ray laser bursts emitted from the solid. [ABSTRACT FROM AUTHOR]

We study recombination processes in nitride LEDs emitting from 270 to 540 nm with EQE ranging from 4% to 70%. We found a significant correlation between the LEDs' electro-optical properties and the degree of nanomaterial disorder (DND) in quantum wells (QWs) and heterointerfaces. DND depends on the nanoarrangement of domain structure, random alloy fluctuations, and the presence of local regions with disrupted alloy stoichiometry. The decrease in EQE values is attributed to increased DND and excited defect (ED) concentrations, which can exceed those of Shockley–Read–Hall defects. We identify two mechanisms of interaction between EDs and charge carriers that lead to a narrowing or broadening of electroluminescence spectra and increase or decrease EQE, respectively. Both mechanisms involve multiphonon carrier capture and ionization, impacting EQE reduction and efficiency droop. The losses caused by these mechanisms directly affect EQE dependencies on current density and the maximum EQE values for LEDs, regardless of the emission wavelength. Another manifestation of these mechanisms is the reversibility of LED degradation. Recombination processes vary depending on whether QWs are within or outside the space charge region of the p-n junction. [ABSTRACT FROM AUTHOR]

The influence of the collective and quantum effects on the Shannon information entropy for atomic states in dense nonideal plasma was investigated. The interaction potential, which takes into account the effect of quantum non-locality as well as electronic correlations, was used to solve the Schrödinger equation for the hydrogen atom. It is shown that taking into account ionic screening leads to an increase in entropy, while taking into account only electronic screening does not lead to significant changes. [ABSTRACT FROM AUTHOR]

A silicon‐based room temperature (RT) continuous wave (CW) operation quantum well (QW) laser emitting at 850 nm is reported in this article. By applying the dislocation filter superlattice, the threading dislocation density of the GaAs pseudosubstrate on Si is reduced to 1.8 × 107 cm−2. The metal‐organic chemical vapor deposition‐grown laser structure with GaAs/GaAsP QW and InAlAs active region dislocation blocking layer are fabricated into broad‐stripe Fabry–Perot laser diodes. A typical threshold current and threshold current density of 286 mA and 715 Acm−2 are obtained with 2 mm cavity length and 20 um stripe width samples. A 94.2 mW single‐facet output power lasing around 854 nm and a 0.314 WA−1 slope efficiency is measured under RT CW operation. After a 10‐min aging process, the tested laser can operate stably under continuous operation conditions at RT and the lifetime can be approximated using an exponential fitting curve, indicating a good life reliability of this QW laser. [ABSTRACT FROM AUTHOR]

This paper introduces and investigates a class of noncommutative spacetimes that I will call "T-Minkowski," whose quantum Poincaré group of isometries exhibits unique and physically motivated characteristics. Notably, the coordinates on the Lorentz subgroup remain commutative, while the deformation is confined to the translations (hence the T in the name), which act like an integrable set of vector fields on the Lorentz group. This is similar to Majid's bicrossproduct construction, although my approach allows the description of spacetimes with commutators that include a constant matrix as well as terms that are linear in the coordinates (the resulting structure is that of a centrally extended Lie algebra). Moreover, I require that one can define a covariant braided tensor product representation of the quantum Poincaré group, describing the algebra of N-points. This also implies that a 4D bicovariant differential calculus exists on the noncommutative spacetime. The resulting models can all be described in terms of a numerical triangular R-matrix through RTT relations (as well as RXX, RXY, and RXdX relations for the homogeneous spacetime, the braiding, and the differential calculus). The R-matrices I find are in one-to-one correspondence with the triangular r-matrices on the Poincaré group without quadratic terms in the Lorentz generators. These have been classified, up to automorphisms, by Zakrzewski, and amount to 16 inequivalent models. This paper is the first of a series, focusing on the identification of all the quantum Poincaré groups that are allowed by my assumptions, as well as the associated quantum homogeneous spacetimes, differential calculi, and braiding constructions. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN) high-electron-mobility transistors (HEMTs) on β-gallium oxide (β-Ga2O3) wafers with various back barrier (BB) materials have garnered considerable attention, mainly due to the superior sheet charge density achieved by the confinement of a large number of electrons in the quantum well, which improves RF performance even further. This work investigates the role of different BB materials of Fe-doped AlGaN buffer AlN/GaN HEMTs on β-Ga2O3 wafers (substrate) with gate–source (LGS) and gate–drain (LGD) distances of 0.4 µm and 1.2 µm, respectively. When compared to traditional substrates such as silicon carbide and silicon, a β-Ga2O3 substrate is more affordable, is accessible in large wafer sizes, and has a lower lattice mismatch (0.4–2.4%) with AlGaN alloys. The effects of gate length scaling (Lg = 50 nm, 100 nm, and 150 nm) on the proposed HEMT devices were also analysed. The short-channel effects can be mitigated by introducing BB structures, which helps avoid further scaling of the barrier layer. With a p-diamond BB of 100 nm thickness, an Fe-doped AlGaN buffer rectangular gated AlN/GaN HEMT Lg = 50 nm results in maximum ID of 5.23 A/mm, gm of 1723 mS/mm, and fT of 361.6 GHz. This superior DC/RF performance can be achieved due to the large confinement of charge carriers into the quantum well and the low leakage current achieved by introducing BB structures and Fe-doped AlGaN buffer. With this outstanding performance, the proposed HEMT device is a promising candidate for next-generation RF applications. [ABSTRACT FROM AUTHOR]

Nitrilotris(methylenephenylphosphinic) acid (NTPAH3) was silylated using hexamethyldisilazane to produce the tris(trimethylsilyl) derivative NTPA(SiMe3)3. From the latter, upon alcoholysis in chloroform, NTPAH3 could be recovered. Thus, a new modification of that phosphinic acid formed. Meanwhile, NTPAH3 synthesized in aqueous hydrochloric acid crystallized in the space group P3c1 with the formation of O-H⋅⋅⋅O H-bonded networks (NTPAH3P), in chloroform crystals in the space group R3c formed (NTPAH3M), the constituents of which are individual molecules with exclusively intramolecular O-H⋅⋅⋅O hydrogen bonds. Both solids, NTPAH3P and NTPAH3M, were characterized by single-crystal X-ray diffraction, multi-nuclear (1H, 13C, 31P) solid-state NMR spectroscopy, and IR spectroscopy as well as quantum chemical calculations (both of their individual constituents as isolated molecules as well as in the periodic crystal environment). In spite of the different stabilities of their constituting molecular conformers, the different crystal packing interactions rendered the modifications of NTPAH3P and NTPAH3M similarly stable. In both solids, the protons of the acid are engaged in cyclic (O=P–O–H)3 H-bond trimers. Thus, the trialkylamine N atom of this compound is not protonated. IR and 1H NMR spectroscopy of these solids indicated stronger H-bonds in the (O=P–O–H)3 H-bond trimers of NTPAH3M over those in NTPAH3P. [ABSTRACT FROM AUTHOR]

In 1971, Zel'dovich predicted the amplification of electromagnetic (EM) waves scattered by a rotating metallic cylinder, gaining mechanical rotational energy from the body. This phenomenon was believed to be unobservable with electromagnetic fields due to technological difficulties in meeting the condition of amplification that is, the cylinder must rotate faster than the frequency of the incoming radiation. Here, we measure the amplification of an electromagnetic field, generated by a toroid LC-circuit, scattered by an aluminium cylinder spinning in the toroid gap. We show that when the Zel'dovich condition is met, the resistance induced by the cylinder becomes negative implying amplification of the incoming EM fields. These results reveal the connection between the concept of induction generators and the physics of this fundamental physics effect and open new prospects towards testing the Zel'dovich mechanism in the quantum regime, as well as related quantum friction effects. The Authors measure the amplification of electromagnetic waves scattered by a rotating metallic cylinder, gaining mechanical rotational energy from the body, as predicted by Zel'dovich in 1971. [ABSTRACT FROM AUTHOR]

Deep ultraviolet light-emitting diodes (DUV LEDs) typically suffer from strong parasitic absorption in the p-epitaxial layer and rear metal contact/mirror. This problem is exacerbated by a substantial portion of the multiple quantum well (MQW) emissions having a strong out-of-plane dipole component, contributing to emission in widely oblique directions outside the exit cone of the front semiconductor emitting surface. To address this, we propose an architecture that leverages such a heavily oblique angular emission profile by utilizing spaced-apart or scattered volume emitter micropixels that are embedded in a low-index dielectric buffer film with a patterned top surface. This approach achieves high light extraction efficiency at the expense of enlarging the effective emission area, however, it does not require a high-index (e.g., sapphire) substrate or a lens or a nanotextured epi for outcoupling purposes. Hybrid wave and ray optical simulations demonstrated a remarkable larger than three to sixfold increase in light extraction efficiency as compared to that of a conventional planar LED design with a sapphire substrate depending on the assumed epi layer absorption, pixel size, and ratio of light emission area to the MQW active area. An extraction efficiency three times greater than that of a recent nanotextured DUV LED design was also demonstrated. This architecture paves the way for DUV LEDs to have a plug efficiency comparable to that of mercury lamps while being significantly smaller. [ABSTRACT FROM AUTHOR]

Silicon is indisputably the most advanced material for scalable electronics, but it is a poor choice as a light source for photonic applications, due to its indirect band gap. The recently developed hexagonal Si1−xGex semiconductor features a direct bandgap at least for x > 0.65, and the realization of quantum heterostructures would unlock new opportunities for advanced optoelectronic devices based on the SiGe system. Here, we demonstrate the synthesis and characterization of direct bandgap quantum wells realized in the hexagonal Si1−xGex system. Photoluminescence experiments on hex-Ge/Si0.2Ge0.8 quantum wells demonstrate quantum confinement in the hex-Ge segment with type-I band alignment, showing light emission up to room temperature. Moreover, the tuning range of the quantum well emission energy can be extended using hexagonal Si1−xGex/Si1−yGey quantum wells with additional Si in the well. These experimental findings are supported with ab initio bandstructure calculations. A direct bandgap with type-I band alignment is pivotal for the development of novel low-dimensional light emitting devices based on hexagonal Si1−xGex alloys, which have been out of reach for this material system until now. Authors demonstrate the synthesis and characterization of direct bandgap quantum wells in the hexagonal Si1−xGex system. Photoluminescence experiments show light emission up to room temperature, and the emission wavelength can be tuned by thickness of the wells and the Si composition. [ABSTRACT FROM AUTHOR]

The paper presents a wide-bandwidth, low-polarization semiconductor optical amplifier (SOA) based on strained quantum wells. By enhancing the material gain of quantum wells for TM modes, we have extended the gain bandwidth of the SOA while reducing its polarization sensitivity. Through a combination of tilted waveguide design and cavity surface optical thin film design, we have effectively reduced the cavity surface reflectance of the SOA, thus decreasing device transmission losses and noise figure. At a wavelength of 1550 nm and a drive current of 1.4 A, the output power can reach 188 mW, with a small signal gain of 36.4 dB and a 3 dB gain bandwidth of 128 nm. The linewidth broadening is only 1.032 times. The polarization-dependent gain of the SOA is below 1.4 dB, and the noise figure is below 5.5 dB. The device employs only I-line lithography technology, offering simple fabrication processes and low costs yet delivering outstanding and stable performance. The designed SOA achieves wide gain bandwidth, high gain, low polarization sensitivity, low linewidth broadening, and low noise, promising significant applications in the wide-bandwidth optical communication field across the S + C + L bands. [ABSTRACT FROM AUTHOR]

Thermodynamical systems having negative heat capacity are characterised by peculiar behaviours, yet they have been reported in several systems ranging from large to nanoscales. We show that negative heat capacity may arise in low-dimensional/nano quantum oscillators due to strong electron correlations observed in underdoped cuprates and quantum wells with negative density of states which emerge in several quantum systems including mesoscopic systems. [ABSTRACT FROM AUTHOR]

Polarization-insensitive semiconductor optical amplifiers (SOAs) in all-optical networks can improve the signal-light quality and transmission rate. Herein, to reduce the gain sensitivity to polarization, a multi-quantum-well SOA in the 1550 nm band is designed, simulated, and developed. The active region mainly comprises the quaternary compound InGaAlAs, as differences in the potential barriers and wells of the components cause lattice mismatch. Consequently, a strained quantum well is generated, providing the SOA with gain insensitivity to the polarization state of light. In simulations, the SOA with ridge widths of 4 µm, 5 µm, and 6 µm is investigated. A 3 dB gain bandwidth of >140 nm is achieved with a 4 µm ridge width, whereas a 6 µm ridge width provides more output power and gain. The saturated output power is 150 mW (21.76 dB gain) at an input power of 0 dBm but increases to 233 mW (13.67 dB gain) at an input power of 10 dBm. The polarization sensitivity is <3 dBm at −20 dBm. This design, which achieves low polarization sensitivity, a wide gain bandwidth, and high gain, will be applicable in a wide range of fields following further optimization. [ABSTRACT FROM AUTHOR]

A special micro LED whose light emitting area is laid out in a U-like shape is fabricated and integrated with colloidal quantum dots (CQDs). An inkjet-type machine directly dispenses the CQD layer to the central courtyard-like area of this U-shape micro LED. The blue photons emitted by the U-shape mesa with InGaN/GaN quantum wells can excite the CQDs at the central courtyard area and be converted into green or red ones. The U-shape micro LEDs are coated with Al2O3 by an atomic layer deposition system and exhibit moderate external quantum efficiency (6.51% max.) and high surface recombination because of their long peripheries. Low-temperature measurement also confirms the recovery of the external quantum efficiency due to lower non-radiative recombination from the exposed surfaces. The color conversion efficiency brought by the CQD layer can be as high as 33.90%. A further continuous CQD aging test, which was evaluated by the strength of the CQD emission, under current densities of 100 A/cm2 and 200 A/cm2 injected into the micro LED, showed a lifetime extension of the unprotected CQD emission up to 1321 min in the U-shape device compared to a 39 min lifetime in the traditional case, where the same CQD layer was placed on the top surface of a squared LED. [ABSTRACT FROM AUTHOR]

Owing to emission-detection spectral overlap, a quantum well (QW) diode can detect shorter-wavelength photons emitted from another diode sharing the same QW active region. Therefore, a wireless light communication system can be established by using identical QW diodes that function separately as transmitters and receivers. Here, we investigate the irreversibility between light emission and detection of the QW diode and present a time-division multiplexing (TDM) visible light communication (VLC) network using five identical blue QW diodes that are defined by software as transmitters or receivers to achieve real-time TDM-integrated interconnection via the same optical paths. These results indicate the great potential of realizing an advanced TDM VLC network for diverse applications. [ABSTRACT FROM AUTHOR]

This paper aims to assess the power dissipation of a threshold quantizer (TIQ) 2-bit-based comparator using a SWS-FET-based inverter [1-2, 4-5]. Unlike conventional comparators, SWS-based comparator functionalized with TIQ comprises two or more vertically stacked quantum dots or well channels [1–3, 5-6]. Herein, power dissipation analysis of the simulated circuit is carried out using Cadence by integrating the Berkeley Short-Channel IGFET Model (BSIM) and the analog behavioral model (ABM) [1, 3-4, 9]. The transient behavior of the inverter circuit is evaluated using 180 nm technology node. Our results demonstrated a significant reduction in power dissipation which overcome the limitation of previous 4-state logic implementations. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of power dissipation and propagation delay in 2-bit SRAM configurations ranging from 7T to 10T, building upon previous work on 6T 2-bit/4-state SWSFET SRAM designs. The study compares the performance of SWSFET SRAMs with CMOS-based 2-state SRAMs [7], highlighting the former's significant advantages in speed and power consumption. Utilizing Cadence simulations and models such as Analog Behavioral Model (ABM) and EKV (Enz–Krummenacher–Vittoz), the analysis incorporates real-world 0.18- μ m technology considerations. The research explores the design nuances of 7T–10T SRAM configurations using SWS-FETs, leveraging their unique characteristics like vertically stacked quantum well/quantum dot channels. Power dissipation analysis reveals varying trends across different SRAM configurations, with notable shifts in voltage changes during transitions. Similarly, propagation delay assessments showcase diverse durations for different voltage transitions, underscoring the impact of SRAM configuration changes on efficiency and complexity. In addition, parasitic capacitance is crucial for optimizing the performance, power efficiency, and reliability of SRAM cells. In these circuits an internal storage parasitic capacitance of 1 fF has been considered to evaluate its effects through simulation-based analysis during the memory cell design process. The findings contribute valuable insights into the trade-offs involved in SRAM design, particularly concerning power dissipation and propagation delay, and are presented. Overall, this study sheds light on the promising potential of SWS-FETs for enhancing memory circuitry performance. [ABSTRACT FROM AUTHOR]

Engineering conduction-band valley couplings is a key challenge for Si-based spin qubits. Recent work has shown that the most reliable method for enhancing valley couplings entails adding Ge concentration oscillations to the quantum well. However, ultrashort oscillation periods are difficult to grow, while long oscillation periods do not provide useful improvements. Here, we show that the main benefits of short-wavelength oscillations can be achieved in long-wavelength structures through a second-order coupling process involving Brillouin-zone folding induced by shear strain. We finally show that such strain can be achieved through common fabrication techniques, making this an exceptionally promising system for scalable quantum computing. [ABSTRACT FROM AUTHOR]

Efficient photovoltaic devices must be efficient light emitters to reach the thermodynamic efficiency limit. Here, we present a promising prospect of perovskite photovoltaics as bright emitters by harnessing the significant benefits of photon recycling, which can be practically achieved by suppressing interfacial quenching. We have achieved radiative and stable perovskite photovoltaic devices by the design of a multiple quantum well structure with long (∼3 nm) organic spacers with oleylammonium molecules at perovskite top interfaces. Our L-site exchange process (L: barrier molecule cation) enables the formation of stable interfacial structures with moderate conductivity despite the thick barriers. Compared to popular short (∼1 nm) Ls, our approach results in enhanced radiation efficiency through the recursive process of photon recycling. This leads to the realization of radiative perovskite photovoltaics with both high photovoltaic efficiency (in-lab 26.0%, certified to 25.2%) and electroluminescence quantum efficiency (19.7 % at peak, 17.8% at 1-sun equivalent condition). Furthermore, the stable crystallinity of oleylammonium-based quantum wells enables our devices to maintain high efficiencies for over 1000 h of operation and >2 years of storage. Efficient radiation is essential to reach thermodynamic limit of photovoltaic efficiency. Here, authors design thick quantum barriers to suppress interfacial quenching and boost photon recycling in perovskite cells, achieving high radiation and photovoltaic efficiencies and long device stability. [ABSTRACT FROM AUTHOR]

In Josephson diodes the asymmetry between positive and negative current branch of the current-phase relation leads to a polarity-dependent critical current and Josephson inductance. The supercurrent nonreciprocity can be described as a consequence of the anomalous Josephson effect —a φ0-shift of the current-phase relation— in multichannel ballistic junctions with strong spin-orbit interaction. In this work, we simultaneously investigate φ0-shift and supercurrent diode efficiency on the same Josephson junction by means of a superconducting quantum interferometer. By electrostatic gating, we reveal a direct link between φ0-shift and diode effect. Our findings show that spin-orbit interaction in combination with a Zeeman field plays an important role in determining the magnetochiral anisotropy and the supercurrent diode effect. The authors study the intrinsic superconducting diode effect (SDE) in a single Josephson junction consisting of a InGaAs/InAs/InGaAs quantum well as the weak link, and an Al film as the superconductor. They find a correspondence between SDE and an offset in the relationship between critical current and the difference in phase of the superconducting order parameter across the junction. [ABSTRACT FROM AUTHOR]

In our pursuit of high-power terahertz (THz) wave generation, we propose innovative edge-terminated single-drift region (SDR) multi-quantum well (MQW) impact avalanche transit time (IMPATT) structures based on the AlxGa1−xN/GaN/AlxGa1−xN material system, with a fixed aluminum mole fraction of x = 0.3. Two distinct MQW diode configurations, namely p+-n junction-based and Schottky barrier diode structures, were investigated for their THz potential. To enhance reverse breakdown characteristics, we propose employing mesa etching and nitrogen ion implantation for edge termination, mitigating issues related to premature and soft breakdown. The THz performance is comprehensively evaluated through steady-state and high-frequency characterizations using a self-consistent quantum drift-diffusion (SCQDD) model. Our proposed Al0.3Ga0.7N/GaN/Al0.3Ga0.7N MQW diodes, as well as GaN-based single-drift region (SDR) and 3C-SiC/Si/3C-SiC MQW-based double-drift region (DDR) IMPATT diodes, are simulated. The Schottky barrier in the proposed diodes significantly reduces device series resistance, enhancing peak continuous wave power output to approximately 300 mW and DC to THz conversion efficiency to nearly 13% at 1.0 THz. Noise performance analysis reveals that MQW structures within the avalanche zone mitigate noise and improve overall performance. Benchmarking against state-of-the-art THz sources establishes the superiority of our proposed THz sources, highlighting their potential for advancing THz technology and its applications. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have garnered significant attention in recent years due to their atomically thin structure and unique electronic and optoelectronic properties. To harness their full potential for applications in next-generation electronics and photonics, precise control over the dielectric environment surrounding the 2D material is critical. The lack of nucleation sites on 2D surfaces to form thin, uniform dielectric layers often leads to interfacial defects that degrade the device performance, posing a major roadblock in the realization of 2D-based devices. Here, we demonstrate a wafer-scale, low-temperature process (<250 °C) using atomic layer deposition (ALD) for the synthesis of uniform, conformal amorphous boron nitride (aBN) thin films. ALD deposition temperatures between 125 and 250 °C result in stoichiometric films with high oxidative stability, yielding a dielectric strength of 8.2 MV/cm. Utilizing a seed-free ALD approach, we form uniform aBN dielectric layers on 2D surfaces and fabricate multiple quantum well structures of aBN/MoS2 and aBN-encapsulated double-gated monolayer (ML) MoS2 field-effect transistors to evaluate the impact of aBN dielectric environment on MoS2 optoelectronic and electronic properties. Our work in scalable aBN dielectric integration paves a way towards realizing the theoretical performance of 2D materials for next-generation electronics. Here, the authors demonstrate a wafer-scale, low-temperature process using atomic layer deposition, for the synthesis of uniform, conformal amorphous boron nitride (aBN) thin films. They further fabricate aBN-encapsulated monolayer MoS2 field-effect transistors. [ABSTRACT FROM AUTHOR]

Effects of postgrowth high-temperature annealing on vacancy complexes and photoluminescence (PL) from GeSiSn/Si multiple quantum wells (MQWs) are studied. The series of PL peaks related to the vacancy-tin complexes was observed for as-grown samples including different structures, such as GeSiSn/Si MQWs, multilayer periodic structure with GeSiSn quantum dots (QDs), GeSn cross-structures upon GeSiSn/Si MQWs, and thick GeSiSn layers. The PL band intensity is significantly reduced after annealing at 700 °C corresponding to the reduction in vacancy density, as demonstrated by the positron annihilation spectroscopy (PAS) data. Such annealing also results in the appearance of the PL signal related to the interband optical transitions in GeSiSn/Si MQWs. However, the high temperature could negatively impact the sharpness of heterointerfaces due to Sn diffusion, thus limiting the PL efficiency. To improve the luminescence properties of GeSiSn/Si structures, we proposed a two-stage technique combining both the annealing and subsequent treatment of samples in a hydrogen plasma at 200 °C. The plasma treatment significantly reduces the PL band of vacancy-related defects, whereas annealing at a moderate temperature of ∼600 °C prevents the blurring of heterointerfaces. As a result, we demonstrate an increase in the relative efficiency of interband PL of type II GeSiSn/Si MQW structures emitting in the range of 1.5–2 μm. [ABSTRACT FROM AUTHOR]

This investigation explores the structural and electronic properties of low-temperature-grown (InAs)4(GaAs)3/Be-doped InAlAs and InGaAs/Be-doped InAlAs multiple quantum wells (MQWs), utilizing migration-enhanced epitaxy (MEE) and conventional molecular beam epitaxy (MBE) growth mode. Through comprehensive characterization methods including transmission electron microscopy (TEM), Raman spectroscopy, atomic force microscopy (AFM), pump–probe transient reflectivity, and Hall effect measurements, the study reveals significant distinctions between the two types of MQWs. The (InAs)4(GaAs)3/Be-doped InAlAs MQWs grown via the MEE mode exhibit enhanced periodicity and interface quality over the InGaAs/Be-InAlAs MQWs grown through the conventional molecule beam epitaxy (MBE) mode, as evidenced by TEM. The AFM results indicate lower surface roughness for the (InAs)4(GaAs)3/Be-doped InAlAs MQWs by using the MEE mode. Raman spectroscopy reveals weaker disorder-activated modes in the (InAs)4(GaAs)3/Be-doped InAlAs MQWs by using the MEE mode. This originates from utilizing the (InAs)4(GaAs)3 short period superlattices rather than InGaAs, which suppresses the arbitrary distribution of Ga and In atoms during the InGaAs growth. Furthermore, pump–probe transient reflectivity measurements show shorter carrier lifetimes in the (InAs)4(GaAs)3/Be-doped InAlAs MQWs, attributed to a higher density of antisite defects. It is noteworthy that room temperature Hall measurements imply that the mobility of (InAs)4(GaAs)3/Be-doped InAlAs MQWs grown at a low temperature of 250 °C via the MEE mode is superior to that of InGaAs/Be-doped InAlAs MQWs grown in the conventional MBE growth mode, reaching 2230 cm2/V.s. The reason for the higher mobility of (InAs)4(GaAs)3/Be-doped InAlAs MQWs is that this short-period superlattice structure can effectively suppress alloy scattering caused by the arbitrary distribution of In and Ga atoms during the growth process of the InGaAs ternary alloy. These results exhibit the promise of the MEE growth approach for growing high-performance MQWs for advanced optoelectronic applications, notably for high-speed optoelectronic devices like THz photoconductive antennas. [ABSTRACT FROM AUTHOR]

This document is a compilation of articles and reviews focused on III-nitride materials, their properties, growth, and applications. The articles cover a range of topics including the optimization of light extraction efficiency in deep-ultraviolet LEDs, the growth and optical properties of InGaN/GaN quantum wells, the investigation of GaN/MoS2 heterostructures, the physical and electrical properties of vertical GaN Schottky diodes, and the fabrication of p-GaN gate HEMTs. Other topics include carrier energy and potential height in GaAs/InGaAs MQW structures, the growth of aluminum nitride thin films, crack-free AlGaN/AlN/GaN HEMT structures, carbon-doped semi-insulating N-polar GaN, and the influence of wet treatment on red microLEDs. The reviews discuss enhanced GaN HEMTs and the growth conditions and external quantum efficiency of InGaN LEDs. The document provides valuable insights into the research and development of III-nitride materials and their applications. [Extracted from the article]

InGaAs/GaAsSb "W" quantum wells with GaAsP barriers are grown on GaAs (001) substrates by molecular beam epitaxy. We investigate the effect of the Sb composition in GaAsSb on the photoluminescence (PL) wavelength. X-ray rocking curve (XRC) measurements and simulations are performed to investigate the material composition and layer thickness. Low-temperature PL spectra are consistent with the XRC results. At the lowest Sb composition of 6%, the PL intensity is the strongest, and room-temperature PL is realized at ∼1100 nm. By increasing the Sb composition in the GaAsSb layer, low-temperature (20 K) PL emits at longer wavelength up to ∼1400 nm at 21% Sb while the PL intensity is the weakest. The XRC is also degraded. The strained bandgap simulation reveals the type-I to type-II band alignment transition as the Sb composition is ≥9%. [ABSTRACT FROM AUTHOR]

This study explores the effects of growth temperature of InGaN/GaN quantum well (QW) layers on indium migration, structural quality, and luminescence properties. It is found that within a specific range, the growth temperature can control the efficiency of In incorporation into QWs and strain energy accumulated in the QW structure, modulating the luminescence efficiency. Temperature-dependent photoluminescence (TDPL) measurements revealed a more pronounced localized state effect in QW samples grown at higher temperatures. Moreover, a too high annealing temperature will enhance indium migration, leading to an increased density of non-radiative recombination centers and a more pronounced quantum-confined Stark effect (QCSE), thereby reducing luminescence intensity. These findings highlight the critical role of thermal management in optimizing the performance of InGaN/GaN MQWs in LEDs and other photoelectronic devices. [ABSTRACT FROM AUTHOR]

The emission spectra of InGaN/GaN white light emitting diodes (WLEDs) were measured. The main emission components were a LED blue line with λmax = 443 nm and a wide double band in the range of 500…650 nm of the secondary emission of AIT-YAG phosphor (Ce). The observed non-monotonic temperature dependence of the emission was attributed to the electric-field screening effect by mobile carriers as well as to thermal quenching due to the increased density of the phonon gas. The power conversion factor of phosphor emission increased in the temperature range of 200…290 K. The total energy losses for the Stokes shift were 82% and 77% for the first (blue) and the second band, respectively. The decrement of emission at high injection currents (over 20 mA) was attributed to ballistic transfer of carriers above the quantum wells and subsequent non- radiative recombination in the barrier layers. The existence of long-term relaxation processes in the white LEDs was assumed to be due to the accumulation of In atoms. Electron beam irradiation caused WLED efficiency degradation due to the introduction of deep traps in the quantum well region. The radiation resistance of the AIT-YAG phosphor was ~1.6 times higher than that of the InGaN part. [ABSTRACT FROM AUTHOR]