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An algorithm for solving exciton Schrodinger equation in an arbitrary 2D multiple quantum well structure under applied electric field is proposed, allowing one to model both the absorption and refraction spectra consistently and efficiently. It gives much better quantitative results than variational approximation, while being faster than more advanced methods. The algorithm is implemented using R language and tested by comparing to other published results. Possible improvements are discussed.

We demonstrate hole-transport-layer-free light-emitting diodes (LEDs) based on solution-processed multiple-quantum-well (MQW) perovskite. The MQW perovskite can self-assemble to a unique structure of vertically graded distribution with two-dimensional layered perovskite covered by three-dimensional-like perovskite at top, which can naturally form a barrier of electron transporting to the anode interface, thereby enhancing the charge capture efficiency. This leads to hole-transport-layer-free MQW perovskite LEDs reaching an external quantum efficiency (EQE) of 9.0% with emission peak at 528 nm, which is over 6 times of LEDs based on three-dimensional perovskite with the same device structure, representing the record EQE of hole-transport-layer-free perovskite LED.

Background: Energy is a major concern in every aspect of our life. Solar energy is a renewable environmentally friendly source of energy. Therefore, solar cells are vastly studied with different technology and different material. Objective: The main objective here is to analyze InGaN material for solar cell applications with less complicated structures of MQW solar cells on revising solar cell with the recombination structure, I-V characteristics, and its efficiency. Methods: The device is simulated using SILVACO ATLAS, where the well and the barrier layers are inserted in the depletion region employing material combination of InGaN / GaN, which increases the solar cell performance parameter. This work focuses on the photogeneration rate, recombination in the active region as well as its current-voltage relation from the simulation. Results: With the increase in the number of QW periods in the active region of the device, the photovoltaic parameters especially conversion efficiency, increases significantly. Under space AM0 solar illumination, the cell efficiency increases up to 8.2 % for 20 MQWs with 20% Indium content for the InGaN/GaN structure. It enhances the External Quantum Efficiency (EQE) upto 36% at nearly 380nm wavelength range near the UV region. Conclusion: The modelled structure is efficiently simulated using TCAD SILVACO ATLAS, and the material Indium Gallium Nitride semiconductor shows an excellent solar cell performance with high solar radiation. It is also observed that with an increase in the number of well periods the solar cell performance increases, which demonstrates the feasibility of Indium Gallium Nitride solar cell with an additional MQW period as a power source.

Improving current injection into r- and m-planes of nanowires (NWs) is essential to realizing efficient GaInN/GaN multiple quantum shell (MQS) NW-based light-emitting diodes (LEDs). Here, we present the effects of different p-GaN shell growth conditions on the emission characteristics of MQS NW-LEDs. Firstly, a comparison between cathodoluminescence (CL) and electroluminescence (EL) spectra indicates that the emission in NW-LEDs originates from the top region of the NWs. By growing thick p-GaN shells, the variable emission peak at around 600 nm and degradation of the light output of the NW-LEDs are elaborated, which is attributable to the localization of current in the c-plane region with various In-rich clusters and deep-level defects. Utilizing a high growth rate of p-GaN shell, an increased r-plane and a reduced c-plane region promote the deposition of indium tin oxide layer over the entire NW. Therefore, the current is effectively injected into both the r- and m-planes of the NW structures. Consequently, the light output and EL peak intensity of the NW-LEDs are enhanced by factors of 4.3 and 13.8, respectively, under an injection current of 100 mA. Furthermore, scanning transmission electron microscope images demonstrate the suppression of dislocations, triangular defects, and stacking faults at the apex of the p-GaN shell with a high growth rate. Therefore, localization of current injection in nonradiative recombination centers near the c-plane was also inhibited. Our results emphasize the possibility of realizing high efficacy in NW-LEDs via optimal p-GaN shell growth conditions, which is quite promising for application in the long-wavelength region.

InGaN/GaN multiple quantum-well (MQW) structures with a wavelength range of green were successfully grown on a c-plane GaN template with SiO2 stripe patterns along the [11-20] and [1-100] directions as a mask. The surface morphologies of both samples were investigated using scanning electron microscopy and demonstrated anisotropic growth characteristics of GaN. The optical characteristics were investigated using Raman spectra and photoluminescence (PL). The InGaN/GaN MQW structure grown on the GaN template with SiO2 stripes along the [1-100] orientation exhibited less stress and higher PL intensity. Transmission electron microscopy results indicated that portions of MQWs were grown on an inclined semipolar plane, and air voids occurred only when the direction of the mask stripe was along the [1-100] orientation. The enhancement of the optical characteristic was due to the air-void structure and inclined semipolar quantum-well sidewalls.

It is well known that carrier distribution in InGaN multiple quantum wells (MQWs) can be significantly inhomogeneous. However, the conventional ABC recombination model assumes that carriers are uniformly distributed throughout the MQW. In this paper, a modified ABC model that considers the unequal carrier density in the QWs was developed. From the analysis of the developed ABC model, the effective recombination coefficients and modified internal quantum efficiency (IQE) were obtained for an arbitrary carrier distribution in MQWs. The efficiency droop was found to be aggravated as the carrier distribution was increasingly inhomogeneous. However, it was also found that the effect of inhomogeneous carrier distribution alone was not sufficient to explain the IQE droop with the theoretical Auger recombination coefficient based on indirect Auger processes. The developed ABC model is expected to provide insight into the influence of inhomogeneous carrier distributions in MQWs on the efficiency droop in GaN-based light-emitting diodes.

Ultrathin engineered metasurfaces loaded with multiple quantum wells (MQWs) form a highly efficient platform for nonlinear optics. Here we discuss different approaches to realize mid infrared metasurfaces with localized second-harmonic generation based on optimal metasurface designs integrating engineered MQWs. We first explore the combination of surface lattice resonances and localized electromagnetic resonances in nanoresonators to achieve very large field concentrations. However, when we consider finite size effects, the field enhancement drops significantly together with the conversion efficiency. To overcome this shortcoming, we explore nonetched L-shaped dielectric nanocylinders and etched arrow-shaped nanoresonators that locally support multiple overlapped resonances maximizing the conversion efficiency. In particular, we show the realistic possibility to achieve up to 4.5% efficiency for a normal incident pump intensity of 50 kW/cm2, stemming from inherently local phenomena, including saturation effects in the MQW. Finally, we present a comparison between pros and cons of each approach. We believe that our study provides new opportunities for designing highly efficient nonlinear responses from metasurfaces (MSs) coupled to MQW and to maximize their impact on technology.

We evaluate the eigenvalues of a type of one-dimensional PT-symmetric fractional Schrodinger equation with multiple quantum wells potential profile. By using a finite-difference scheme, we solve the fractional Schrodinger equation and present the algorithm. We study the effects of different parameters on the pairwise coalescence of eigenvalues. We show that by using the mentioned parameters, we can tune the position of the pairwise coalescence of the eigenvalues and the surface area between the two eigenvalues that intersect. An interesting phenomenon is that a small value of the fractionality as much as 0.15 can destroy the pairwise coalescence of eigenvalues and produce a single energy level. We also, consider the Hofstadter butterfly of a PT-symmetric one-dimensional system and show that by increasing the intensity of the potential imaginary part, we can kill the butterfly.

We demonstrate a novel biaxially tensile-strained Ge/SiGe multiple quantum well (MQW) electroabsorption modulator with low polarization dependence. The device is waveguide integrated and has a length of 900 μm. Suspended microbridge structure is utilized to introduce biaxial tensile strain to the Ge/Si0.19Ge0.81 MQWs. Light is coupled into and out of the waveguide through deeply etched facets at the ends of the waveguide. Both TE and TM polarized electroabsorption contrast ratios are tested by the use of polarization maintaining focusing lensed fiber and a linear polarizer. A polarization irrelevant contrast ratio of 4.3 dB is achieved under 0 V/2 V operation. Both simulations and experiments indicate that the demonstrated device has potential in waveguide integrated utilizations that have high requirements on polarization uniformity.

In this study, spin polarization efficiency and spin-dependent transmission of electrons passing through a multiple quantum well structure with constant total effective length (60 nm) made of GaAs/Al0.3Ga0.7As, which was grown along [001] direction, were investigated. The calculations were done with the quantum transmitting boundary method. We presented the number of wells in a constant total length as a tuning tool for spin filtering purposes. In some energy intervals, 100% spin polarization and spin-dependent transmission were observed.

We explore the effect of the sub-well centers and related carrier dynamics mechanisms in dislocation-free DUV AlGaN/AlGaN multiple quantum wells (MQWs) homoepitaxially grown on AlN substrate. Cross...

Optical properties of AlGaN UVC multiple-quantum-wells (MQWs) with nanoscale inverted polarity domains are strongly related to the polar surfaces and nanoscale structures. In this work, the impact ...

The photoluminescence (PL) characteristics of two violet light-emitting InGaN/GaN multiple quantum well structures with different GaN barrier thickness, grown by metalorganic chemical vapor deposition, are investigated. It is found that for the sample with thick GaN barrier layers, the polarization effect in InGaN quantum wells is promoted. According to the temperature-dependent PL measurements, it is considered that the localization effect in a thick-barrier sample is enhanced which may be attributed to the increased growth time of GaN barrier layers. It is surprising to observe that at low temperatures, the PL spectral widths of the thick-barrier sample are smaller than those of the thin-barrier sample, although the distribution of In content in InGaN well layers may be more inhomogeneous for the thick-barrier sample.

We report here an optically pumped deep UV edge emitting laser with AlGaN multiple quantum wells (MQWs) active region grown on AlN substrate by low pressure organometallic vapor phase epitaxy (LP-OMVPE) in a high-temperature reactor. The 21 period Al0.53Ga0.47N/Al0.7Ga0.3N MQWs laser structure was optically pumped using 193 nm deep UV excimer laser source. A laser peak was achieved from the cleaved facets at 280.3 nm with linewidth of 0.08 nm at room temperature with threshold power density of 320 kW/cm2. The emission is completely TE polarized and the side mode suppression ratio (SMSR) is measured to be around 14 dB at 450 kW/cm2.

The temperature dependence of the spectra of photoluminescence (PL) from a blue InGaN/GaN multiplequantum-well (MQW) structure is investigated at lower excitation power. Two emission peaks, related to InGaN and assigned to In-rich quasi-quantum dots (QDs) and InGaN-matrix in the full PL spectrum, were observed. Upon increasing the temperature, both PL peak linewidths exhibited "double-W-shaped" (narrowing–broadening–narrowing–broadening–narrowing–broadening) temperature dependence. Combined with the observed features of the temperature dependences of the PL intensities, the temperature-dependent behaviors in this case can be interpreted as the relaxation and thermalization of carriers inside respective phase structures and the transfer of carriers between two phase structures, because of the strong phase separation and significant component fluctuation in the InGaN well layers.

The performance of a Multiple Quantum Well (MQW) Heterojunction Bipolar Transistor Laser (HBTL) has been studied using GeSn alloy. Both symmetric and asymmetric quantum wells have been considered. Main analysis is focused on finding the minority carrier concentration in the base, the base threshold current, light output power of the device and the values are compared with GeSn based Single Quantum Well and InGaAs based Multiple Quantum Well Transistor Laser.

Both the weak carrier confinement in InGaN/GaN multiple quantum wells (MQWs) and the severe quantum-confined Stark effect in InGaN/AlGaN MQWs limit the improvement of quantum efficiency for near-ultraviolet (UV) light-emitting diodes (LEDs). In this regard, we have demonstrated high quantum efficiency LEDs grown on 4 inch Si substrates with well-designed InGaN/GaN/AlGaN/GaN MQWs. On the one hand, the proposed GaN interlayer barrier can increase the concentration and the spatial overlap of carriers in the MQWs for modulating the energy band and polarization theoretically. On the other hand, the GaN interlayer barrier grown by two-step temperature control can effectively improve the quality of the MQWs. The as-fabricated 395 nm near-UV LED chips with InGaN/GaN/AlGaN/GaN MQWs reveal an external quantum efficiency of 60% and a light output power of 659 mW at an injection current of 350 mA. This work provides a valuable solution to obtain high quantum efficiency and high power near-UV LEDs.

We proposed a compact electroabsorption modulator based on a multimode interference waveguide (MMI-EAM). Owing to both electroabsorption and electrorefractive effects in an InGaAlAs/InAlAs multiple quantum well core layer, an extinction ratio of as high as 39 dB can be obtained in the 1.55 µm wavelength region with wavelength independence.