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This letter introduces a simple technique to reduce cross polarization in multilayer antipodal linearly tapered slot antenna taking advantage of the slab air-filled substrate integrated waveguide (SAFSIW) topology. The operation mechanism is presented together with simulations and experimental validations. The measured results show a reflection coefficient lower than –17 dB over the Ka -band. A measured gain of 13 ± 1.35 dBi is observed in the overall Ka -band. The proposed broadband structure achieves a measured cross-polarization isolation of better than 16.07 dB at endfire direction over the Ka -band, which is a significant improvement compared to its multilayer AFSIW implementation counterpart.

This article introduces two-way broadband air-filled substrate integrated waveguide (AFSIW) isolated power dividers/combiners based on surface mounted absorbing materials. The proposed structures take advantage of the AFSIW multilayer feature. The absorber implementation is found highly tolerant of variations in dimensions and positioning. Three different power dividers/combiners topologies are analyzed theoretically, simulatively, and experimentally. The measurement results validate the broadband responses of the fabricated Ka-band demonstrators. The proposed power dividers/combiners are intended to exploit high-power AFSIW system on substrate (up to few hundred watts).

International audience; We hereby present a new equivalent circuit model including both lumped and distributed elements for GCPW-MS transitions (GCPW for Grounded CoplanarWaveguide and MS for Microstrip). In order to validate the modelling results, such transitions have been fabricated on a 20 μm-thick BCB (Benzocyclobutene resin) substrate using grounding pads including via-holes of different diameters. The study focused on the impact of the via-hole diameter on the performance of the transition and more specifically on its bandwidth. The transitions were made using a simple technological process based on photosensitive polymer. ADS simulation data of the new equivalent circuit model were in very good agreement with measured S-parameters. Both theoretical and experimental results have shown that the bandwidth of such a transition can reach up to 100 GHz using via-holes of 900 μm diameter.

This letter introduces stepped-impedance bandpass filters based on the slab air-filled substrate integrated waveguide (SAFSIW), which provides a compromise in terms of loss and footprint between substrate integrated waveguide (SIW) and air-filled SIW (AFSIW). First, the theoretical unloaded quality factor of the SAFSIW guided-wave structure is presented. Then, a design procedure of SAFSIW stepped-impedance bandpass filters is introduced. Finally, for demonstration purposes, a third-order Chebyshev filter, centered at 30 GHz, is synthesized, optimized, fabricated, and measured. With a low-cost FR-4 to enclose the structure, a return loss better than 15 dB with a minimum insertion loss of 0.99 dB in the passband is obtained in experiments.

International audience; Zinc tin nitride (ZnSnN2) is a promising semiconductor candidate for solar cell applications and optoelectronic devices. However, the practical use of this material has been limited by several issues as, among others, oxygen contamination, a very high concentration of free carriers and the difficulty to reach the theoretically predicted band gap. Here, we deposit thin films of ZnSnN2 by reactive DC magnetron co-sputtering at room temperature with a RF bias power (Pb) in the range of 0-50 W. Using first principle calculations, we explore the structural and opto-electronic properties that are favorably compared to experimental results. We demonstrate that the optical band gap energy can be decreased from 1.7 eV to 1.34 eV, close to the predicted value of 1.37 eV. The free electron concentration is decreased down to 10 17 cm-3 which results in the reduction of the absorption by free electrons in the IR range. In addition, in a given range of applied bias powers, we observe a densification of the films and a significant decrease of their oxygen contamination from 6.7 down to 2.0 at. %. The study underlines that a value of 20 W power bias leads to the optimal structural, optical and electrical properties. Our results provide an interesting method to obtain a potential candidate for photovoltaic applications, in an environmental friendly way, for a low-cost industrialization.

International audience; Although solar cells operate under illumination, most electrical characterization methods are carried out in darkness, which implies some bias. In this work, we study the influence of light on the contact resistivity of the electron and hole contacts of a silicon heterojunction (SHJ) cell using the transfer length method (TLM) method in order to determine them in conditions representative of an operating solar cell at maximum power point. A specific fabrication process has been developed to preserve the passivation level. Therefore, we first focus on the patterning approach used for processing, and show that we can fabricate TLM samples with good passivation properties. Using simulations, we also discuss on the influence of inhomogeneities in the excess minority carrier spatial concentration on the TLM analysis. These inhomogeneities, due to shading, local damages in the passivation or to carrier drift under bias voltage make the measurement complicated to carry out without significant error. Our results suggest that the measurement is more precise in darkness and at very high injection levels, under rear illumination and a low voltage bias.

International audience; Surface plasmon resonance (SPR) sensing is a well-established high-sensitivity, label-free and real-time detection technique for biomolecular interaction study. Its primary working principle consists of the measurement of the optical refractive index of the medium that is in close vicinity of the sensor surface. Bio-functionalization techniques allow biomolecular events to be located in such a way. Since optical refractive indices of any medium varies with the temperature, the place where the measurement takes place shall be within a temperature-controlled environment in order to ensure any temperature fluctuation is interpreted as a biomolecular event. Since the SPR measurement probes the sensed medium within the penetration depth of the plasmonic wave, which is less or in the order of 1 µm, we propose to use the metallic film constituting the detection surface as a localized heater aiming at controlling finely and quickly the temperature of the sensed medium. The Joule heating principle is then used and the modeling of the heater is reported as well as its validation by thermal IR imaging. Using water as a demonstration medium, SPR measurement results at different temperatures are successfully compared to the theoretical optical refractive index of water versus temperature.

International audience; This article presents a detailed study of the optical behavior of a leaky waveguide deflector in view of its utilization as key component to create a new solution for an analog to digital converter, capable to achieve very high data conversion rate (up to 40 giga sample per second). We present here the different works that we went through using software based on BPM (Beam Propagation Method) and FDTD (Finite Difference Time Domain) to determine the phase and amplitude characteristics of the leaky optical field. These pieces of information are indispensable to design of a diffractive optical lens to focus the leaky beam. As the results between theory and simulation are in good agreement, the next steps are to realize and finalize the component.

International audience; Based on several semiconductor research, we have studied one of the new semiconductors, due to its exciting physical proprieties that in turn solve some problems in the photovoltaic’s industry. We have divided this work into two parts. The first part, is to study the optical proprieties of ZnSnN2, as calculation of the absorption coefficient, bandgap, reflection coefficient, and transmission coefficient. As for the second part, a study of some parameters that affect the efficiency of p-CuCrO2 (CCO)/ n-ZnSnN2 (ZTN) solar cell using SCAPS-1D software, and our results are compared with the results of another software (wxAMPS), where results showed great compatibility with the presence of weak uncertainty. We have studied the influence of many parameters such as the thickness of the absorber layer (n-ZnSnN2), the thickness of the buffer layer (p-CuCrO2), the temperature, the series resistance (Rs), the shunt resistance (Rsh) and the defect density on the performance of ZnSnN2 solar cells which included in the real device. The photovoltaic parameters have been calculated using AM1.5G solar irradiance at the intensity of one sun, a temperature of 300 K, and considering the flat band condition at the interface. We have been achieving a high-efficiency of η ≈ 22% without defects. Given the characteristics of this new semiconductor ZnSnN2, which composed of earth-abundant, non-toxic and inexpensive element, as well as a high absorption coefficient, it can be considered as an alternative for PV and optoelectronic applications.

In this paper, we describe a novel fabrication method of a microfluidic integrated surface plasmon resonance (SPR) gold chip based on a (3-mercaptopropyl) trimethoxy silane (MPTMS) self-assembled monolayer. This monolayer was formed at the surface of a microfluidic chip made of polydimethylsiloxane (PDMS). Its presence was confirmed by contact angle and Fourier transform infrared spectroscopy measurements on the modified PDMS surface. A basic, but nevertheless appropriate, 4-channel microfluidic system was made on PDMS and reported on a gold SPR sensor. Sealing tests were carried-out by injecting continuous flows of solutions under gradient pressure up to 1.8 bar. Bonding strength of chemical and corona binding were measured and compared. The test of the integrated microfluidic SPR sensor on an SPR bench validated its functionality and proved as well that no leakage is observed between the different microfluidic channels.

In this paper, the design flexibility of multilayer air-filled substrate integrated waveguide (AFSIW) technology is examined and exploited to introduce a -3 dB power divider with isolated outputs based on a balanced-delta-port magic-tee topology. To overcome the inherent poor isolation provided by lossless three-port junctions, discrete resistors are implemented using the low-cost and standard surface mount device (SMD) process and commercially available off-the-shelf components (COTS). Theoretical, simulated, and experimental results of the proposed self-packaged wideband power divider with isolated outputs are presented. To the authors' best knowledge, this is the first time that an AFSIW integrating surface mounted components is reported. The measured results show that the output return loss and isolation are better than 10 dB over 28% bandwidth (centered at 35 GHz). A maximum amplitude imbalance of 0.69 dB together with a maximum phase imbalance of 4.2° are obtained in measurements. This proposed divider is envisioned by the authors to be deployed in system on substrate (SoS) for many wireless applications where low loss and high power handling capability are desired such as antenna beamforming networks and amplifier modules.

ZnSnN2 is a member of ternary Zn-IV-N2 semiconductors, where IV = Si, Ge or Sn. According to theoretical calculations and preliminary experimental results, Zn-IV-N2 semiconductor materials afford same bandgap range than III-nitride semiconductors. It is also expected similar electronic and optical properties as for InGaN, for example, direct bandgaps and large optical absorption coefficients [1][2]. Based on first-principles calculations, ZnSnN2 becomes a promising material for photovoltaic. Exhibiting a bandgap value around 1.7 - 2 eV, it can provide an interesting alternative furnishing an inorganic thin film solution for tandem cell over silicon [3]. The most stable wurtzite-derived structure of bulk ZnSnN2 was given to be the orthorhombic Pna21 phase by calculating the total energy per unit cell, band structure and electronic density of states [4]. ZnSnN2 can be synthesized from various methods, in which sputtering technique tends to dominate. The primary advantages of using sputtering are high deposition rates, application for most materials, high-purity and adhesive films, ability to coat heat-sensitive substrates (glass substrates, plastic substrates) and automation capabilities [5]. It provides, moreover, a realistic way of integration with Si based bottom cells. By changing the experiment conditions, band gap can expand to 2 eV [6], n-type carrier concentration obtained 7.01x1017cm3 and high mobility receive up to 15.5 cm2/V.s [7]. In this work, ZnSnN2 thin films were produced on glass substrates by co-sputtering Zn and Sn targets at room temperature in a reactive atmosphere of argon, nitrogen and hydrogen. By changing the composition of this atmosphere, the optical and electrical properties of material are changed. The morphology and crystal structure were investigated by using SEM, AFM and X-ray diffraction. The optical band gap ranges from 1.8eV to 2.5 eV and was deduced from UV-VIS spectroscopy. The n-type carrier concentration was measured between 2.5e17 to 2.4e20 cm-3, and the highest carried mobility is 2.0 cm2/V.s. First photoconductive samples were fabricated and tested under solar simulator. Measurement gave a photocurrent value of 148mA/cm2. These results are promising ones for the potential application of ZnSnN2 material as a photovoltaic absorber. References: [1] A. Punya, W. R. L. Lambrecht, and M. Van Schilfgaarde, “Quasiparticle band structure of Zn-IV-N2 compounds,” Phys. Rev. B - Condens. Matter Mater. Phys., vol. 84, no. 16, pp. 1–10, 2011. [2] A. Punya., T. R. Paudel, and W. R. L. Lambrecht, “Electronic and lattice dynamical properties of II-IV-N2 semiconductors,” Phys. Status Solidi C, vol. 8, no. 7, pp. 2492–2499, 2011. [3] T. P. White, N. N. Lal, and K. R. Catchpole, “Tandem solar cells based on high-efficiency c-Si bottom cells: Top cell requirements for >30% efficiency,” IEEE J. Photovoltaics, vol. 4, no. 1, pp. 208–214, 2014. [4] L. Lahourcade, N. C. Coronel, K. T. Delaney, S. K. Shukla, N. A. Spaldin, and H. A. Atwater, “Structural and optoelectronic characterization of RF sputtered ZnSnN 2,” Adv. Mater., vol. 25, no. 18, pp. 2562–2566, 2013. [5] S. Swann, “Magnetron sputtering,” Phys. Technol., vol. 19, no. 6, pp. 67–75, 1988. [6] N. Feldberg et al., “Growth, disorder, and physical properties of ZnSnN2,” Appl. Phys. Lett., vol. 103, no. 4, 2013. [7] K. kumar Chinnakutti, V. Panneerselvam, and S. Thankaraj Salammal, “Tailoring optoelectronic properties of earth abundant ZnSnN2 by combinatorial RF magnetron sputtering,” J. Alloys Compd., vol. 772, pp. 348–358, 2019.

International audience; In this paper, we are interested in simulating and modeling of Cds/ZnSnN2 structure for a solar cell using SCAPS-1D. The ZnSnN2 is considered as one of the promising absorber materials for photovoltaic application due to the high optical efficiency and the low cost. In the present work, we have investigated the effects of the thickness of the buffer and the absorber layers, the temperature on electrical parameters (Voc) the open-circuit voltage and (Jsc) the short-circuit current density, (FF) fill factor and (η) efficiency of the solar cell. The results show a remarkable improved of the efficiency a η = 26.49% under the AM1.5G spectrum, one sun and deformation of 0.51% between the Cds and the ZnSnN2. The achieved results show that the ZnSnN2 is a very promising material for thin film photovoltaics and offers a number of interesting advantages compared to (CIGS) and (CZTS) due to its high efficiency, earth-abundant, non-toxic and inexpensive element

International audience; This paper presents an optimization and simulation of optical and electrical properties of GaAsPN/GaAs tandem Dual-Junction solar cells such as current density-voltage (J-V), external quantum efficiency (EQE), with an AM1.5 solar spectrum. We comparing the simulated performance of various N fractions and we will show that the use of N=0.01 improve the performances of external quantum efficiency (EQE) and current-voltage characteristics. Our results have been shown that an optimal efficiency of about 26.19% was obtained with P composition x=0.37 and N fractions y=0.01. In addition, a doping of 2.1018 cm-3 of the GaAs0.62P0.37N0.1 base top cell boosts the efficiency from 25.73% to 26.19%.

International audience; This paper aims to improve the performance of graded ultrathin CIGS-based solar cells using the one-dimensional simulation program (SCAPS-1D). In this context, we have assessed the effect of the graded bandgap and the thickness of the absorber layer (CIGS) on solar cell performance. We have also examined the impact of different graded bandgap profiles by varying the gallium concentration. Notably, the increase of the gallium concentration (xGa) and the CIGS thickness (dCIGS) have degraded the conversion efficiency η. The optimization of these parameters gives a considerable solar yield when dCIGS = 1 μm and xGa in the range 0.1–0.3. For the graded cell, we have mentioned that the double-graded profile improves significantly the conversion efficiency up to 22.21% compared to the uniform profile with η = 21.43%.

This paper describes a numerical study of ultrathin CIGS solar cell using the one-dimensional simulation program. The various properties of the absorber layer such as the band gap energy, the absorption coefficient, and the reflection coefficient are investigated. In addition, the impact of adding silicon to reduce the thickness of CIGS is also examined. We have carried out a theoretical study to show the influence of the thickness and the gallium concentration of the CIGS absorber layer on the performance of the Mo/Si/CIGS/ZnS/ZnO structure. It has been demonstrated that increasing xGa and dCIGS affect the conversion efficiency, FF, Voc, and Jsc. Finally, we have achieved a conversion efficiency η = 21.08% with an optimal value of gallium content equal to 20%when the thickness of the absorber layer has been reduced to 0.75 μm. This study allowed us to improve the performance of thin film solar cell.

In this paper, we are interested in simulations and modeling of ZnGeN 2 /GaN quantum wells solar cell, like all other solar cells as we know always are sensitive to the temperature, many effects like number of quantum wells (NQWs), temperature (T) on photovoltaic properties such as current density-voltage I(V), power density-voltage P(V) and the external quantum efficiency (EQE) are investigated. The most parameter affected by the change in temperature is the open circuit voltage (Voc). We found in a temperature of 280 K gives better results of open circuit voltage (V oc ), maximum power output (P m ), and conversion efficiency $(\eta)$ their values are 2.87 V, 21.12 mW/cm2’ and 21.22% respectively.

This paper aims to model and simulate a new quantum dot solar cell (QDSC), based on GaAs 1-x Nx/GaAs. In this work, we have studied different effects such as the influence of the concentration of nitrogen, number of quantum dots inserted on the current-voltage J- V and the external quantum efficiency (EQE) of our structure. Our results have shown that the optimal nitrogen content is 3%. With 30 GaAs 1-x Nx/GaAs QDs layers, relative enhancements of about 7.91 % and 8% of short-circuit current and efficiency achieved, respectively. In addition, the use of 30 layers of QDs increases the maximum of EQE from 85.45% to 96.88%. Therefore, the embedded QDs bring positive effects and help to improve the performance of the solar cell.

International audience; This paper reports simulations of gradual bandgap CIGS absorber and its impact on the characteristics of a solar cell. The bandgap of the CIGS absorber varies linearly and drops from Egmax (at the junction limit) to Egmin (in the vicinity of the rear contact).We introduce an effective absorption coefficient based on this variation. We will demonstrate that this gradual profile contributes to an improvement up to 171 mV of the open circuit voltage Voc of the cell that is linked to the modification of the internal electrical field distribution within the absorber. However, a joint reduction of 1.50 mA/cm2 of short circuit current density, Jsc, is observed. Overall, the conversion efficiency increases from 19.2%, for a uniform bandgap absorber structure, to 24.9% in that case of gradual bandgap. Additionally, we investigate the impact of absorber thickness and temperature on cell characteristics

International audience; In this work, we have studied and simulated nanostructures to improve the solar cell efficiency. The idea of this study is to insert multi-quantum wells in the structure of a solar cell (MQWSC). The electric field, recombination, and the photogeneration rates of charge carriers in QWSC influence the collection and carrier extraction efficiency. In this work, the behavior of these magnitudes and the main characteristics as current density-voltage J-V and external quantum efficiency of In0.35Ga0.65N/GaN MQWSC are studied. Our results have shown that the insertion of five MQW layers within the intrinsic region of p-GaN/i-InGaN/n-GaN heterojunction solar cell can increase both short-circuit current and the conversion efficiency from 0.89 to 2.12 mA/cm2 and 0.78 to 1.25%, respectively; additionally, with the same number of embedded MQWs, the absorption range edge of the heterojunction solar cell extends from 430 to 500 nm.

Considering the chalcopyrite solar cell fabrication process, the commonly reported substrate bending effect that is observed after thermal process, in a front side halogen lamp-based annealing configuration (Rapid Thermal Annealing –RTA- equipment), has been investigated. We first proposed a simple model explaining the substrate bending shape dependence on the initial stress state within the molybdenum (Mo) layer (free, tensile or compressive). Then, we showed that it is possible to overcome this issue by simply using a reactive (oxygen based) sputtering process for the deposition of the Mo layer. Finally, we showed that using a bilayer structure Mo(O)/Mo allows a more precise control of the flatness of the annealed samples. To understand the mechanisms governing such changes in substrate bending, structural and morphological material changes as a function of oxygen flow have been investigated by using X-ray diffraction and scanning electron microscope imaging, respectively. The elemental distribution throughout the Mo(O)/Mo bilayer structure thickness was also investigated.

In this work, a numerical simulation is used to explore and determine the arsenic content profile and effects of the well thickness on the intersubband coefficient of the conduction band in the GaAs x P 1-x /GaP quantum well structure, x is the concentration of arsenic. This theoretical study has shown that the intersubband conduction band and the corresponding wavelength emission are mainly affected by these both factors. Hence, one should adjust the desired energy and achieve a large absorption coefficient by changes the quantum well width and the arsenic composition.

In the first part of this paper, we will show that a sputtering-based fabrication process exhibiting a low environmental footprint has been developed for the fabrication of copper indium gallium selenide (CIGS) absorbing material. Its originality lies in using room temperature sputtering in a pulsed—direct current mode of a single quaternary target followed by a post-anneal. At any stage of the process, selenium or sulfur atmosphere is used. Inert gas is used, respectively argon and a forming gas, for the deposition and annealing step, respectively. CIGS cells have been fabricated using such an absorbing layer. They exhibit an efficiency close to 12%. A tandem cell approach, using a thin film technology in conjunction with the well-established Si technology, is a promising technique, achieving cells with 30%, and higher, efficiency. Such cells are awaited, jointly with a stronger implementation of low environmental footprint technologies, as a vision for 2030. In the first section, sputtering technique has shown its ability to be developed in such a way achieving an environmentally friendly process that can be moreover compatible to be co-integrated with, for example, Si technology. In a second section, we will present a prospective discussion on the materials that can be applied to produce a sustainable approach for such a tandem cell configuration.

This paper focuses on the simulation and optimization of electrical and optical properties such as current density-voltage (J-V), external quantum efficiency (EQE) and the photoluminescence spectra (PL) of InSb/GaAs quantum dot solar cell (QDSC). The InSb QDs have been inserted in the intrinsic region of p-i-n GaAs solar cell. Our results have been shown that 30 InSb/GaAs QD layers provide a relative enhancement of 22.35% and 29.30% of the short-circuit current and the efficiency, respectively. With the same number of the QD layers, the absorption range edge of low energy photons has been extended from 900 to 1400 nm. The electrical features obtained for InSb/GaAs QDSC have been compared with those obtained for InAs/GaAs QDSC in goal to show the better structure. The PL spectra has been also compared with experimental result for the same structure. Moreover, the QDSC has been optimized with respect to the thickness of QDs. The optimal conversion efficiency of 10 QD layers is improved from 14.85% to 18.30% by increasing the thickness of the QDs from 5 nm to 20 nm.

The electrical properties of InAsP/Si quantum dot solar cell (QDSC) are numerically studied and analyzed in this paper. Many effects like number of quantum dot (QD) layers inserted and Arsenic content of InAs x P 1-x on photovoltaic properties such as current density-voltage J-V and the external quantum efficiency (EQE) are investigated. Our results have been shown that the optimal Arsenic content is 0.6. With 30 InAsP/Si QDs layers, relative enhancements of about 7% and 6.70% of short-circuit current and efficiency are achieved, respectively. Otherwise, the absorption range edge of low energy photons was extended from 1120 to 1200 nm. This reveals that introduction of QDs in the intrinsic region of p -i- n Silicon (Si) solar cell enhances significantly the device characteristics beyond what has been reported for conventional semiconductor-based solar cells.

In recent years, the development of quantum well solar cells QWSCs (Quantum Well Solar Cells) has generated a great deal of interest. These configurations have shown good promise to optimize the low conversion efficiency of conventional solar cells because of the high rate of absorption losses present in them. In this work, we are interested in modeling and simulation of two different structures of solar cells, a simple solar cell based on silicon Si and a quantum well solar cell SiGe/Si. When a solar cell is compared to 80 quantum well layers of Si 0.8 Ge 0.2 with a pin solar cell based on Si. The short circuit current J sc increases from 23.55 to 37.48 mA/cm 2 with a relative increase of 59.15% found. In addition, the limit of the absorption band of the lower energy photons extends from 1100 nm to 2000 nm.

In this work, the performance of solar cell based on CdS-n/Cu 2 ZnSnS 4 -p hetero-junction is numerically simulated. The aim of the study is to investigate the influence of thickness, defects density and bandgap energy of absorber layer CZTS and the thickness of the buffer layer CdS of the solar cell on electrical parameters J sc , V oc , FF and efficiency η of the cell. The results of our simulation allowed us to optimize the parameters above mentioned in order to get the best efficiency at the optimal band gap which corresponds to the maximum of the solar spectrum with optimal values of the electrical performances of the cell. This results lead to develop CZTS solar cells with high efficiency and low cost and give a help full indication for fabrication process.

Usually a buffer layer of cadmium sulphide is used in high efficiency solar cells based on Cu(In,Ga)Se2(CIGS). Because of cadmium toxicity, many in-vestigations have been conducted to use Cd-free buffer layers. Our work focuses on this type of CIGS-based solar cells where CdS is replaced by a ZnS buffer layer. In this contribution, AFORS-HET software is used to simulate n-ZnO: Al/i-ZnO/n-ZnS/p-CIGS/Mo polycrystalline thin-film solar cell where the key parts are p-CIGS absorber layer and n-ZnS buffer layer. The characteristics of these key parts: thickness and Ga-content of the absorber layer, thickness of the buffer layer and doping concentrations of absorber and buffer layers have been investigated to optimize the conversion efficiency. We find a maximum conversion efficiency of 26% with a short-circuit current of 36.9 mA/cm2, an open circuit voltage of 824 mV, and a fill factor of 85.5%.

In this aim, we were interested in the optimization and simulation of pin-In1−xGaxN structure and InGaN multi quantum well structures for photovoltaic applications. This ternary alloy which is an III–V semiconductor presents important characteristics especially its gap energy, thus, the increase of the photons absorption of wavelengths. It has been shown that the increase in indium concentration increases the current density Jsc and the maximum output power. In return, the Voc decreases consequently. For In0.50Ga0.50N structure we observed that the current density and the maximum power are respectively around 19.50 mA/cm2 and 27.50 mW/cm2 with a ratio of 21.65 mA/cm2. Also it is shown that the incorporation of the quantum well in the active region results in an increase of Jsc and Pmax but Voc remains unchanged. The incorporation of 50 quantum well structure in the In0.50Ga0.50N gives 22 mA/cm2 of the current density and 32 mW/cm2 of the maximum output power. The use of the structure based on In0.50Ga0.50N (MQW) induces an efficiency of 32%. We deduced that the relative efficiency is improved by 10.9%.

This work deals with the modeling and optimization of the CuInGaSe/CdS based structure for photovoltaic applications. We took into consideration the effect of the gallium concentration and the temperature on the strain, band gap energy, absorption and efficiency of the structure. It has been demonstrated that increasing the gallium concentration increases the ban gap energy, while increasing temperature decreases it. These two parameters vary the efficiency significantly. For x = 30% and T = 300 K, the band gap energy is equal to 1.15 eV with a deformation of 0.5% and efficiency around 20%. We have also found that at this value of the band gap energy the structure absorbs most of the incident photons. Then to achieve a reliable cell based on CuInGaSe/CdS it is adequate to find a compromise between the gallium concentration in the alloy, the temperature and the strain.

This paper presents a 90° self-compensating phase shifter based on a slab air-filled substrate integrated waveguide platform in Ka-band. A shorter phase shifter is obtained due to its operation mechanism. The measurement shows a relative phase shift of 88 ± 7.8°, or around 8.9% for phase error, and an amplitude imbalance of 0.06 ± 0.14 dB over Ka-band. A theoretical study is presented together with simulation to understand the operation principle of this phase shifter. Simulation and measurement results are compared and discussed.

International audience; In this work, we theoretically investigate the structural dependence of intersubband absorption of InGaAsSb/GaAs single quantum well structures. We begin by analyzing the impact of In and Sb incorporation on the critical thickness, conduction band offset and band gap energy. The first two electron energy levels E12 and the corresponding wavelength were made for the InxGa1−xAs1-ySby/GaAs system and are analyzed in detail by solving the Schrödinger equation. Also, we have investigated effects of composition and well width on the intersubband absorption. In addition, the wavelength and absorption coefficient of the ISBT can be adjusted and optimized by changing the composition and the width of the SQW. Finally, strain effects on intersubband absorption and on the peak response wavelength have also been systematically studied. Our study shows that InGaAsSb/GaAs SQW will play a key role in research of electronics and photonic devices in the future.

International audience; This work investigates the influence of the ion source (Au+ and Si+2 ions) of liquid metal alloy source-focused ion beam (LMAIS/FIB) on the nanopattering. Two sets of SiO2/Si nanopatterns with a width of 450 nm on Silicon on insulator (SOI) substrate are fabricated by 30 keV Au+ and Si+2 ions, respectively. To study this effect, the sputtering yield is calculated using the volume loss method from atomic force microscopy (AFM) profiles obtained for each set. The results of the sputtering yield were compared with theoretical results calculated from Yamamura model for normal incidence for validation. The comparison showed a good agreement between the two results with a relative difference of about 5.3% obtained using Si+2 ions.

International audience; Nanoporous gold and platinum electrodes are used to pattern n-type silicon by contact etching at the macroscopic scale. This type of electrode has the advantage of forming nanocontacts between silicon, the metal and the electrolyte as in classical metal assisted chemical etching while ensuring electrolyte transport to and from the interface through the electrode. Nanoporous gold electrodes with two types of nanostructures, fine and coarse (average ligament widths of ∼30 and 100 nm, respectively) have been elaborated and tested. Patterns consisting in networks of square-based pyramids (10 ×10 µm 2 base × 7 µm height) and U-shaped lines (2, 5, and 10 µm width × 10 µm height × 4 µm interspacing) are imprinted by both electrochemical and chemical (HF-H 2 O 2) contact etching. A complete pattern transfer of pyramids is achieved with coarse nanoporous gold in both contact etching modes, at a rate of ∼0.35 µm min −1. Under the same etching conditions, U-shaped line were only partially imprinted. The surface state after imprinting presents various defects such as craters, pores or porous silicon. Small walls are sometimes obtained due to imprinting of the details of the coarse gold nanostructure. We establish that np-Au electrodes can be turned into "np-Pt" electrodes by simply sputtering a thin platinum layer (5 nm) on the etching (catalytic) side of the electrode. Imprinting with np Au/Pt slightly improves the pattern transfer resolution. 2D numerical simulations of the valence band modulation at the Au/Si/electrolyte interfaces are carried out to explain the localized aspect of contact etching of n-type silicon with gold and platinum and the different surface state obtained after patterning. They show that n-type silicon in contact with gold or platinum is in inversion regime, with holes under the metal (within 3 nm). Etching under moderate anodic polarization corresponds to a quasi 2D hole transfer over a few nanometers in the inversion layer between adjacent metal and electrolyte contacts and is therefore very localized around metal contacts.

International audience

The aim of this work based on modeling and simulation is to study the effect of indium (In) incorporation on the optoelectronic properties of structures In x Ga 1-x N/GaN, In x Ga 1-x N/Al 2 O 3 and In x Ga 1-x N/Si. In this study we simulated the impact of (In) on the strain, and the band gap where we applied solid model for band gap energy calculation of the alloys In x Ga 1-x N/GaN, In x Ga 1-x N/Al 2 O 3 and In x Ga 1-x N/Si. Also we used the empirical models to calculate the critical thickness and the absorption coefficient. The optoelectronic properties of this heterostructures as a function of (In) concentration are calculated and compared with the experimental data where we find that the incorporation of (In) induce band gap reduction, which change considerably the absorption, also influences epitaxial limits where we can develop nanoscale layers which opens the way to more efficient cells. But these changes vary according to the substrate used where we observe that each substrate has advantages over other substrates. This study allows us to improve the efficiency of solar cells using InGaN ternary alloy lattice matched to GaN, Al 2 O 3 or Si substrate.

In order to attest the feasibility and the concept of great-quality III – V devices, we focus our actual work on the developming of a tandem dual-junction solar cell, including a GaAS 1−x P x top cell and a Si bottom cell. A simulation study of the top cell was performed. The impact of GaAS 1−x P x absorber layer thicknesses, the temperature, and P composition x on cell efficiency are evidenced. In these structures, a tunnel junction was needed to interconnecting both the bottom and top cell. We comparing the simulated performance of two tunnel junction structure and we will show that the use of the GaAs (n+)/GaAs (p+) tunnel junction improve the performance of the currentvoltage characteristics. An optimal efficiency of about 16.27% was obtained with a thickness of about 1–m, P fraction x=0.37 and a temperature of 285 K.

International audience; The aim of this modeling and simulation is to study the influence of the incorporation of nitrogen (N) and aluminum (Al) on the optoelectronic properties of the structure AlxGa1-xAs1-yNy/Ge, and then choose the right combination (N, Al) which gives us a better conversational efficiency of the junction(AlxGa1-xAs1-yNy/Ge), in this study, we simulated the effect of N and Al on the strain, the band gap, carrier mobility and structure efficiency where we based on theoretical models experimentally validate, It has been shown that the Al concentration slightly affects the stress and the band gap, but it has a significant influence on the incorporation of nitrogen and in a more homogeneous way introducing a dramatic decrease in the band gap what change considerably the absorption, carrier mobility and final yield of the structure

International audience; In this work we report a modeling and optimization of a novel core (p-GaN)-multishell (i-InxGa1-xN/i-GaN/n-Al0.1Ga0.9N/n-GaN) coaxial NWs with a total length of about 3 μm and a radius of 0.19 μm. The variation of Indium composition in the i-InxGa1-xN active layer shows that x = 15% is the optimal composition that gives a good short circuit current and efficiency of about 2.24 mA/cm2 and 2.93%, respectively. Beyond x = 35% the structure starts to present deteriorations. Moreover, the optimal x composition founded provides a gain of about 12.9% of EQE in the mid-infrared part. The study of the variation of the total current density along the nanowire demonstrates that the maximum of this latter is located in AlGaN cladding shell layer and at the interfaces between the i-region and AlGaN cladding shell layer. In other hand, our results show that our structure presents an optimal efficiency of about 3.5% at a temperature of 275 K with the same AM1.5G solar spectrum.

A pulsed-DC sputtering process at room temperature has been developed for the deposition of the CIGS absorber layer. It uses a single quaternary target and is followed by a high temperature post-deposition annealing process. It has to be particularly noticed that no additional selenium supply was used. The annealed layers have shown a high microstructural quality: micrometric grain size, highly oriented (112) chalcopyrite phase, no phase decomposition and no Cu2-xSe secondary phase at the surface. The use of such an absorber layer for the fabrication of 0.5 cm2 solar cells has allowed reaching a conversion efficiency of 11.8% with an open circuit voltage of 558 mV, a short circuit current density of 32.1 mA·cm−2 and a fill factor of 65.8%.

International audience; This paper focuses on the simulation and optimization of electrical and structural properties of high efficiency InGaP/InGaAs/Ge triple junction solar cells that incorporate In0.7Ga0.3As quantum dots with in the GaAs middle cell material. Current density-voltage (J-V), external quantum efficiency (EQE) and capacitance-voltage (C-V) characteristics have been simulated and discussed. Results show that 30 pairs of In0.70Ga0.30As (QD)/GaAs (barrier) in the middle cell provide a relative enhancement of 13% in EQE in the 900–1000 nm wavelength range. This leads to a short-circuit current of 20 mA/cm2, an open circuit voltage of 2.3 V, a fill factor of 81.73%, and a conversion efficiency of 39.03%. The C-V revealed that a relatively high number of interfacial states are present in the 3-J cell structure including the QD layers, which decreases the open circuit voltage. In this study we benefited 18% of relative efficiency.

This work focuses on the modeling and optimization of a structure based on InGaP/InGaAs/InGaAsN/Ge for photovoltaic. In this study we took into consideration the concentration effect of alloys x (In) and y (N) on the strain, the bandgap, the absorption and structure efficiency. It has been shown that the concentration of indium varies the strain and the bandgap. These two parameters change considerably the yield. Also it optimized the effect of alloys on the total absorption of the structure. For a concentration of indium x = 0.40 and y = 0.03 we had a absorption coefficient which is equal to 2 × 10 6 cm −1 . We have found 50% efficiency for the multi-junction structure based on In 0.55 Ga 0.45 P/In 0.40 Ga 0.60 As/In 0.30 Ga 0.70 As 0.97 N 0.03 /Ge. To achieve a reliable high efficiency multi-junction structure, we just need to optimize the concentrations of different alloys.

Room temperature deposited aluminium-doped zinc oxide thin films on glass substrate, using pulsed-DC magnetron sputtering, have shown high optical transmittance and low electrical resistivity with high uniformity of its spatial distribution after they were exposed to a rapid thermal annealing process at 400 °C under N2H2 atmosphere. It is particularly interesting to note that such an annealing process of AZO thin films for only 30 s was sufficient, on one hand to improve their optical transmittance from 73% to 86%, on the other hand to both decrease their resistivity from 1.7 × 10−3 Ω cm to 5.1 × 10−4 Ω cm and achieve the highest uniformity spatial distribution. To understand the mechanisms behind such improvements of the optoelectronic properties, electrical, optical, structural and morphological changes as a function of annealing time have been investigated by using hall measurement, UV–visible spectrometry, X-ray diffraction and scanning electron microscope imaging, respectively.

International audience; In this paper, we report a simulation and investigation of a single InxGa1-xN/GaN axial multiple quantum well nanowire (MQWNW) solar cell of radius r = 190 nm and a length of L = 1165 nm. Our results have been shown that 15 In0.15Ga0.85N (QW) /GaN (barrier) periods is the maximum number that our structure can be supported with an optimal efficiency of about 1.65% achieved with ε = 1.5%. The insertion of MQWs in nanowire permits the growth of InxGa1-xN MQWs with high indium concentration of about 50% and ε = 5%. At this indium concentration, the optimal efficiency obtained was 1.70%. Moreover; the structure has been studied with respect to the nanowire radius. In this context, we have shown that the efficiency enhancement achieved through the increase of radius is attributed to the increase of photo-carriers. Study of polarization and proton irradiations has indicated the negative effect of polarization on structure performances and high resistance of III-N semiconductor materials against the radiations, respectively. From these novel structures we can improve solar cell performance for new applications.

The slab air-filled substrate integrated waveguide (SAFSIW) is presented as a compromise between the high performance air-filled substrate integrated waveguide (AFSIW) and low profile dielectric-filled substrate integrated waveguide (DFSIW). Both theoretical and experimental studies are presented in order to investigate SAFSIW structures. To the authors' best knowledge, this is the first time that an SAFSIW-to-DFSIW transition is reported. A 90° phase shifter based on SAFSIW and a patent pending mounting process is also introduced. Measured results show a very high figure of merit (FoM) over the Ka-band. A phase difference of $\mathbf{86}\pm \mathbf{5}.\mathbf{4}^{\pmb{\circ}}$ , an amplitude imbalance of $\mathbf{0}.\mathbf{05}\pm \mathbf{0}.\mathbf{15}\ \mathbf{dB}$ and a FoM of $\mathbf{457}^{\pmb{\circ}}/\mathbf{dB}$ are obtained.

International audience; This work focuses on the study and simulation of a based intersubband GaNAsBi/GaAs quantum well structure. The effect of different physical and optical parameters has been explored. The band gap of GaNAsBi is calculated using the band anti-crossing model. The influence of the composition and the quantum well width on the intersubband transition within the conduction band has been examined and discussed. We will discuss in detail the influence of these structural parameters on the intersubband absorption coefficient. So, two features have been observed: the evolution of characteristics and the shift of the corresponding emission wavelength. Our simulation contributes to designing and fabricating based GaNAsBi/GaAs optoelectronic intersubband devices in the mid infrared region.

In this paper, we are interested in modeling and simulations of InGaN/GaN Quantum Wells Solar Cell, like all other semiconductor devices solar cells are sensitive to temperature, the most parameter affected by the rise in temperature is the open circuit voltage Voc. In this paper, the thermal effects on InGaN/GaN multiple quantum well solar cells (MQWSCs) with an Indium concentration of 0.28 are studied. A temperature of 280 K gives better results of open circuit voltage, maximum power output and conversion efficiency their values are 1.84 V, 24.86 mW/cm2 and 24.87% respectively.

This article aims to modeling and to simulate new solar cells for a photovoltaic application with semiconductor materials III-V, more exactly based of \( InAs_{x} Sb_{1 - x} /GaAs \). We initially studied the influence of the indium concentration on the various alloy parameters GaInAsSb epitaxed on GaInSb substratum. Indeed the increase of the density of indium decreases the band gap of the structure, in order to absorb the maximum of solar spectrum. The study includes results giving the variations of the various factors influencing the efficiency on conversion according to the indium concentration in the structure.

Aluminum doped-zinc oxide (AZO) thin films were prepared on glass substrate by radio-frequency (RF) sputtering at room temperature. The sheet resistance, Rsh [Ω] the resistivity, ρ [Ω·cm] and the 1/f noise were studied as a function of thickness, t from 50 nm to 450 nm. The eddy current characterized the homogeneity of AZO thin films. The surface morphology has been analysed by atomic force microscopy (AFM). The 1/f noise is normalized with respect to the bias, frequency and unit area, and Cus is proportional to the sheet resistance Rsh. Two configurations were used to characterize material and contact noise. The pressure effect of four point-probe on the material and the contact noise were also investigated. Our results show that the homogeneity of the samples increases as the film thickness increases and the resistivity decreases with increasing thickness and reaches the lowest value of 1 × 10− 3 Ω cm at 450 nm. The average grain size and the root-mean-square roughness increases with rising thickness. The ratio K = Cus / Rsh is proportional to t2, which indicates that the mobility and the noise parameter αH shrink with the shrinkage of the thickness.

In this work, we have studied the GaSb/GaAs Quantum Dot Solar Cell for different number of quantum dot layers, the short circuit current, the open circuit voltage, the fill factor and the conversion efficiency are improved with increasing the insertion of quantum dot layers in the intrinsic region; The best values of these parameters are obtained for structure with 30 QD layers. These results are supported by the external quantum efficiency measurements. Then the analysis of the GaSb/GaAs -30 QDSC with temperature change range from 260 K to 400 K indicates that the photovoltaic device performance are degraded when temperature increases such as the open circuit voltage, the fill factor and the conversion efficiency, however the short circuit current shows an enhancement of about 20.24% compared with its value obtained at room temperature.