The composition effect on the bowing parameter in the cubic InGaN, AlGaN and AlInN alloys

Numerical simulation based on FP-LAPW calculations is applied to study direct and indirect band gap energy of the cubic AlxGa₁₋xN, InxGa₁₋xN and InxAl₁₋xN alloys.The direct and indirect band-gap bowing parameter is also calculated, and the values obtained are very important, as we find a strong dependence of the bowing parameter on the composition

Electronic structure and Jahn-Teller effect in GaN:Mn and ZnS:Cr

We present an ab-initio and analytical study of the Jahn-Teller effect in two diluted magnetic semiconductors (DMS) with d4 impurities, namely Mn-doped GaN and Cr-doped ZnS. We show that only the combined treatment of Jahn-Teller distortion and strong electron correlation in the 3d shell may lead to the correct insulating electronic structure. Using the LSDA+U approach we obtain the Jahn-Teller energy gain in reasonable agreement with the available experimental data. The ab-initio results are completed by a more phenomenological ligand field theory.Comment: 15 pages, 5 figure

Integrated through-silicon-via-based inductor design in buck converter for improved efficiency

Introduction. Through-silicon-via (TSV) is one of the most important components of 3D integrated circuits. Similar to two-dimensional circuits, the performance evaluation of 3D circuits depends on both the quality factor and inductance. Therefore, accurate TSV-inductor modeling is required for the design and analysis of 3D integrated circuits. Aim. This work proposes the equivalent circuit model of the TSV-inductor to derive the relations that determine both the quality factor and the inductance by Y-parameters. Methods. The model developed was simulated using MATLAB software, and it was used to evaluate the effect of redistribution lines width, TSV radius, and the number of turns on inductance and quality factor. Additionally, a comparative study was presented between TSV-based inductors and conventional inductors (i.e., spiral and racetrack inductors). Results. These studies show that replacing conventional inductors with TSV-inductors improved the quality factor by 64 % compared to a spiral inductor and 60 % compared to a racetrack inductor. Furthermore, the area of the TSV-inductor was reduced up to 1.2 mm². Using a PSIM simulator, the application of an integrated TSV-inductor in a buck converter was studied, and the simulation gave very good results in 3D integration compared to 2D integration. Moreover, the simulation results demonstrated that using a TSV-inductor in a buck converter could increase its efficiency by up to 15 % and 6 % compared to spiral and racetrack inductors, respectively.Вступ. Наскрізне з’єднання кремнію (TSV) є одним з найважливіших компонентів тривимірних інтегральних схем. Подібно до двовимірних схем, оцінка продуктивності тривимірних схем залежить як від добротності, так і від індуктивності. Тому для проєктування та аналізу тривимірних інтегральних схем необхідне точне моделювання TSV-індуктора. Мета. У цій роботі пропонується еквівалентна модель схеми TSV-індуктора для виведення співвідношень, що визначають як добротність, так і індуктивність за Y-параметрами. Методи. Розроблена модель була змодельована з використанням програмного забезпечення MATLAB та використана для оцінки впливу ширини ліній перерозподілу, радіусу TSV та кількості витків на індуктивність та добротність. Крім того, було представлено порівняльне дослідження між індукторами на основі TSV та звичайними індукторами (тобто спіральними та індукторами типу бігова доріжка). Результати. Ці дослідження показують, що заміна звичайних індукторів на TSV-індуктори покращила добротність на 64 % порівняно зі спіральним індуктором і на 60 % порівняно з індуктором типу бігова доріжка. Крім того, площа TSV-індуктора була зменшена до 1,2 мм². За допомогою симулятора PSIM було вивчено застосування вбудованого дроселя TSV в знижувальному перетворювачі, і моделювання дало дуже хороші результати при 3D-інтеграції порівняно з 2D-інтеграцією. Більш того, результати моделювання показали, що використання TSV-індуктора в понижувальному перетворювачі дозволяє підвищити його ефективність до 15% та 6 % порівняно зі спіральними індукторами та індукторами типу бігова доріжка відповідно

The first principle calculation of electronic and optical properties of AlN, GaN and InN compounds under hydrostatic pressure

Numerical simulation based on FPLAPW calculations is applied to study the lattice parameters, bulk modulus, band energy and optical properties of the zincblende binary solids AlN, GaN, InN under hydrostatic pressure. The results obtained are in a good agreement with experimental and theoretical values

Functional outcomes in symptomatic versus asymptomatic patients undergoing incisional hernia repair: Replacing one problem with another? A prospective cohort study in 1312 patients

Background: Incisional hernias can be associated with pain or discomfort. Surgical repair especially mesh reinforcement, may likewise induce pain. The primary objective was to assess the incidence of pain after hernia repair in patients with and without pre-operative pain or discomfort. The secondary objectives were to determine the preferred mesh type, mesh location and surgical technique in minimizing postoperative pain or discomfort. Materials and methods: A registry-based prospective cohort study was performed, including patients undergoing incisional hernia repair between September 2011 and May 2019. Patients with a minimum follow-up of 3–6 months were included. The incidence of hernia related pain and discomfort was recorded perioperatively. Results: A total of 1312 patients were included. Pre-operatively, 1091 (83%) patients reported pain or discomfort. After hernia repair, 961 (73%) patients did not report pain or discomfort (mean follow-up = 11.1 months). Of the pre-operative asymptomatic patients (n = 221), 44 (20%, moderate or severe pain: n = 14, 32%) reported pain or discomfort after mean follow-up of 10.5 months. Of those patients initially reporting pain or discomfort (n = 1091), 307 (28%, moderate or severe pain: n = 80, 26%) still reported pain or discomfort after a mean follow-up of 11.3 months postoperatively. Conclusion: In symptomatic incisional hernia patients, hernia related complaints may be resolved in the majority of cases undergoing surgical repair. In asymptomatic incisional hernia patients, pain or discomfort may be induced in a considerable number of patients due to surgical repair and one should be aware if this postoperative complication

Optoelectronic, Elastic and Thermal Properties of Cubic Perovskite-Type SrThO₃

The electronic structure, elastic, thermal and optical properties of the cubic strontium thorate SrThO₃ are calculated using the full-potential linearized augmented plane wave method (FP-LAPW) based on the density functional theory with generalized gradient approximations GGA and local density approximation LDA. The modified Becke-Johnson potential (mBJ) is applied in electronic structure for calculating the energy gap. The obtained results are the Young modulus, shear modulus, the Poisson ratio, isotropic shear modulus, longitudinal, transverse and average sound velocities, the Zener anisotropy factor, the Kleinman parameter and the Debye temperature of the systems. All results are discussed and compared with the available experimental data

Influence of the strong field in enhancing, electronic magnetic and optical properties of Mn-doped MgO

International audienceThe local spin density approximation with Hubbard-like coulomb term based on first principles calculations are used to investigate a substitute doping of transition metal Mn in MgO. Under the crystal field theory and according to the intensity of the ligand field, the d(4)-d(8) transition elements can have two possible configurations such as the case of Mn(d(5)), in its low spin configuration that represents a strong field, the Mn+2 doped MgO material has a half-metallic character in the two proposed studies approximations: the local spin density approximation (LSDA) and (LSDA + U), a character that will enable to change the magnetic, electronic and optical properties., This result is supported by the sp-d exchange mechanism calculation confirming that the coupling between impurity and ligand is completely ferromagnetic. The material has a magnetic moment of about 1 mu(B), mainly due to the Mn impurity of around 95% in LSDA + U case. In optical propriety the material shows a slight spin polarization and reduction of band gap of around 5% with strong filed in LSDA + U case. (C) 2017 Elsevier GmbH. All rights reserved

Electronic and optical properties of K-doped ZnO: Ab initio study

International audienceWe present the results of ab initio calculations of K-doped ZnO in the wurtzite structure using a supercell of 32 atoms and density functional theory. A complete analysis of its electronic, optical and magnetic properties is provided. The local spin density approximation (LSDA) has been used to analyze the density of states and to understand the K influence at different concentration values. The material is revealed to become a p-type doped semiconductor. The optical constant or refractive index, the dielectric function, and the absorption coefficient were determined and show a good agreement with available experimental data. Potassium doping leads to an absorption peak at about 380 nm. That peak might improve the absorption characteristics of ZnO for solar cell or optical applications

Ultra-High Concentration Vertical Homo-Multijunction Solar Cells for CubeSats and Terrestrial Applications

This paper examines advances in ultra-high concentration photovoltaics (UHCPV), focusing specifically on vertical multijunction (VMJ) solar cells. The use of gallium arsenide (GaAs) in these cells increases their efficiency in a range of applications, including terrestrial and space settings. Several multijunction structures are designed to maximize conversion efficiency, including a vertical tunnel junction, which minimizes resistive losses at high concentration levels compared with standard designs. Therefore, careful optimization of interconnect layers in terms of thickness and doping concentration is needed. Homo-multijunction GaAs solar cells have been simulated and analyzed by using ATLAS Silvaco 5.36 R, a sophisticated technology computer-aided design (TCAD) tool aimed to ensure the reliability of simulation by targeting a high conversion efficiency and a good fill factor for our proposed structure model. Several design parameters, such as the dimensional cell structure, doping density, and sun concentrations, have been analyzed to improve device performance under direct air mass conditions AM1.5D. The optimized conversion efficiency of 30.2% has been achieved with investigated GaAs solar cell configuration at maximum concentration levels

The manganese effect on the magnetism and optical properties especially interband transitions of zinc sulphide

International audienceThe electronic, magnetic and optical properties of Mn doped zinc sulphide (ZnS:Mn) were calculated with the FP-LAPW method by using the LSDA and LSDA+U approximations. The latter one is shown to be necessary to account for the strong electron correlation in the Mn 3d shell. With the increase of Mn2+ concentration, the band gap is decreased for the spin-up channel and increased for the spin-down channel. Furthermore, to calculate the correct exchange couplings d-d and sp-d of Mn-doped ZnS, we have applied the Hubbard U parameter on Mn-d states. The influence of this Hubbard U parameter on the optical, electronic and magnetic properties of ZnS:Mn is investigated. We found that U=6 eV gives good results for exchange couplings and optical properties close to the experimental ones. The magnetic coupling between neighboring Mn impurities in ZnS is found to be antiferromagnetic. (C) 2016 Elsevier B.V. All rights reserved