Designs of GaN/AlGaN quantum-cascade lasers emitting at 34 and 38 μm (ΔE∼36 meV) are presented, assuming either a- or c-plane crystal growth orientation. In the calculation quasibound state energies wave functions, we account for intrinsic electric field induced by piezoelectric (in case growth) spontaneous polarization. The structures were simulated, their output characteristics extracted, using a fully self-consistent rate equation model with all relevant intra- interperiod scatterings...

Smelting used to be less efficient; therefore, wastes obtained from historical processing at smelter plants usually contain certain quantities of valuable metals. Upon the extraction useful metal elements, metallurgical slag can repurposed as an alternative mineral raw material in building sector. A case study was conducted, which included investigation physico-chemical, mineralogical, and microstructural properties Pb–Zn found historic landfill near Topilnica Veles North Macedonia. The...

The influence of doping density on the performance GaAs∕AlGaAs quantum-cascade lasers is presented. A fully self-consistent Schrödinger–Poisson analysis, based a scattering rate equation approach, was employed to simulate above threshold electron transport in laser devices. V-shaped local field domain formation observed, preventing resonant subband level alignment high pumping-current regime. resulting saturation maximal current, together with an increase limits dynamic working range under...

The development of a thermal model for quantum cascade lasers (QCLs) is presented. used in conjunction with self-consistent scattering rate calculation the electron dynamics an InGaAs-AlAsSb QCL to calculate temperature distribution throughout device which can be limiting factor high operation. investigate effects various driving conditions and geometries, such as epilayer down bonding buried heterostructures, on active region temperature. It found that heterostructures have eight decrease...

A design for a GaN∕AlGaN optically pumped terahertz laser emitting at 34 μm (ΔE∼36meV) is presented. This uses simple three-level scheme where the depopulation of lower level achieved via resonant longitudinal-optical-phonon emission. The quasibound energies and associated wave functions are calculated with intrinsic electric field induced by piezoelectric spontaneous polarizations. structures based on double quantum well were simulated output characteristics extracted using fully...

A detailed theoretical and experimental study of the influence injector doping on output characteristics electron heating in midinfrared GaAs∕AlGaAs quantum cascade lasers is presented. The employed model transport was based a fully nonequilibrium self-consistent Schrödinger-Poisson analysis scattering rate energy balance equations. Three different devices with sheet densities range (4–6.5)×1011cm–2 have been grown experimentally characterized. Optimized arsenic fluxes were used for growth,...

A method for the calculation of electronic structure pyramidal self-assembled InAs/GaAs quantum dots is presented. The based on exploiting exact $\bar{C}_{4}$ symmetry 8-band $k\cdot p$ Hamiltonian with strain taken into account via continuum mechanical model. operators representing group elements were represented in plane wave basis and projectors used to find adapted which corresponding matrix block diagonal four blocks approximately equal size. number total quasi-angular momentum...

A criterion for strain balancing of wurtzite group-III nitride-based multilayer heterostructures is presented. Single and double strain-balanced GaN/AlGaN quantum well structures are considered with regard to their potential application in optoelectronic devices working at communication wavelengths. The results realizable, presented the form design diagrams that give both intersubband transition energies dipole matrix elements terms structural parameters. optimal parameters operating λ∼1.3...

Analysis of carrier transport in cascaded GaAs/AlGaAs, p-Si/SiGe and GaN/AlGaN terahertz structures is performed using self-consistent rate equations with kinetic energy-balance simulations. The electron n-type simulated standard envelope function nonparabolic effective mass approximations all relevant electron–electron electron–optical phonon scattering. In the case GaAs-based model extended to include ionized impurity interface roughness scattering as well. hole subband structure p-type...

The presented work offers a novel process scheme for valorizing historical Pb-Zn slag, which involves crushing, grinding, and then using separation techniques to concentrate valuable components (nonferrous metals). This methodology could have significant impact on the global beneficiation of metallurgical slags since, in theory, it is significantly more simple, environmentally friendly, cost-effective than standard pyrometallurgical or hydrometallurgical procedures. According previous...

A fully quantum-mechanical model for electron transport in quantum-well infrared photodetectors (QWIPs) is presented, based on a self-consistent solution of the coupled rate equations. The important macroscopic parameters like current density, responsivity, and capture probability can be estimated directly from this first-principles calculation. applicability was tested by comparison with experimental measurements GaAs/AlGaAs device, good agreement found. general applied to any other...

A theoretical model of electron transport in quantum cascade lasers subjected to a magnetic field is developed. The Landau level electronic structure was calculated from the envelope-function Schr\"odinger equation within effective-mass approximation. modeled using self-consistent rate-equation description for full period and its interaction with adjacent periods. scattering processes included are electron--longitudinal-optical-phonon, electron--longitudinal-acoustic-phonon,...

The presented work offers an innovative process scheme for valorizing Pb-Zn slag, which involves crushing, grinding, and separation techniques to concentrate valuable components (non-ferrous metals). This methodology could have a significant impact on the global beneficiation of metallurgical slags since it is significantly more simple, environmentally friendly, cost-effective than standard pyro- hydrometallurgical procedures. According previous physicochemical mineralogical studies, slag...

We propose an optically pumped laser based on intersublevel transitions in InAs-GaAs pyramidal self-assembled quantum dots. A theoretical rate equations model of the is given order to predict dependence gain pumping flux and temperature. The energy levels wave functions were calculated using 8-band k/spl middot/p method where symmetry pyramid was exploited reduce computational complexity. Carrier dynamics modeled by taking both electron-longitudinal optical phonon acoustic interactions into...

We report on a detailed experimental and theoretical analysis of the role injector doping density both threshold current (Jth) saturation (Jsat), determining dynamic range quantum cascade lasers. The results were obtained from two growth series λ≈9μm GaAs∕Al0.45Ga0.55As quantum-cascade lasers based single double phonon resonance depopulation mechanisms. derive quasilinear dependence Jth designs for as wide (4–10)×1011cm−2. Despite increase faster rise with in an enhanced up to ∼8×1011cm−2....

Abstract The philosophy behind this work has been to build a predictive “bottom up” physical model of quantum cascade lasers (QCLs) for use as design tool, interpret experimental results and hence improve understanding the processes occurring inside working devices simulator developing new material systems. standard uses envelope function effective mass approximations solve two complete periods QCL under an applied bias. Other models, such k · p empirical pseudopotential, have employed in...

A theoretical model and a design of magnetic-field tunable CdMnTe∕CdMgTe terahertz quantum well infrared photodetector are presented. The energy levels the corresponding wave functions were computed from envelope function Schrödinger equation using effective-mass approximation accounting for Landau quantization giant Zeeman effect induced by magnetic confinement. electron dynamics modeled within self-consistent coupled rate equations approach, with all relevant electron-longitudinal-optical...

Experimental results showing room temperature normal incidence mid-infrared detection by AlGaN/GaN quantum well infrared photodetectors are presented. Designed structures have intersubband transitions corresponding to wavelengths in the region of 3 and 4 µm, where strong absorption a sapphire substrate dominates. The spectra, therefore, were characterized electronic Raman scattering photocurrent spectroscopy. spectra agree with theoretical predictions. Details device fabrication presented...

This paper presents the results of tests carried out to determine how dosage bentonite added as binder, affects properties green pellets made limestone fines that originate from Lithothamnium processing. Bentonite was in different mass fractions (1, 2.5, 5 and 10%), whereas all other parameters pelletizing process remained constant. The aim consolidate form mechanically stable pellets, provided remain unchanged. formed this way were analysed applying DTA/TG analysis FTIR SEM analyses. showed...

A quantum-cascade laser (QCL) thermal model is presented. On the basis of a finite-difference approach, used in conjunction with self-consistent carrier transport to calculate temperature distribution near-infrared InGaAs/AlAsSb QCL. The presented investigate effects driving conditions and device geometries on active-region temperature, which has major influence performance. buried heterostructure combined epilayer-down mounting found offer best performance compared alternative structures...

The design and simulation of an In0.53Ga0.47As∕Al0.56As0.44Sb quantum-cascade laser emitting in the near infrared is presented. Designed using a self-consistent rate equation solver coupled with energy balance equation, proposed has calculated population inversion ∼20% at 77K sufficient gain to achieve room-temperature emission λ∼2.8μm. Threshold currents range 4–8kA∕cm2 are estimated as temperature increases from 77Kto300K. output characteristics compared existing λ∼3.1μm structure...

Abstract This review article surveys the subject of choice high gradient magnetic separation processes for removal Fe 2 O 3 carriers from quartz raw material by electromagnetic separator with field intensity 1.4 T.

This paper investigates grinding of mineral mixtures with different grindabilities in the Bond ball mill. Understanding ore mixture is great importance processing. The energy required for crushing and presented by work index determined means grindability test. presents experimental results values obtained standard method on limestone andesite samples, as well composite samples made up from these weight ratios. Comparatively are shown that mass fraction components make calculation their...