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This paper presents an optically controlled broadband phase-shifter using a parallel-line coupler, that takes advantage of high-resistivity silicon photo-absorption at 840 nm. A continuously variable phase-shifting of 120° is achieved at 11 GHz with Δ|S21| < 5 dB and with |S11| < -15 dB in a large frequency band (6–15 GHz). © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 570–573, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21232 [ABSTRACT FROM AUTHOR]

Abstract: We present a versatile metallic air-bridge process that can be used either for high relief compound semiconductor devices or interconnections schemes. Our technology uses conventional contact photolithography and does not require dry-etching techniques allowing a fast fabrication time, reliable production and cost effectiveness. It is based on the use of only one photoresist and one electroplating step. [Copyright &y& Elsevier]

This paper deals with the 3D modeling of the photo-induced load created by a laser that illuminates a semiconductor substrate. This independent optical command allows us to change the microwave behavior of the microstrip device. We present a 3D-equivalent microwave model for the photo-injection in terms of equivalent conductivity plasma. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 356–359, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11380 [ABSTRACT FROM AUTHOR]

The optically controlled phase and magnitude of a coplanar transmitted wave have been investigated, taking advantage of the benefit of silicon photo-absorption at 843 nm. A phase-shift of 45° has been achieved at 12 GHz while the magnitude remains constant. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 129–132, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10993 [ABSTRACT FROM AUTHOR]

Candida albicans mannan consists of a large repertoire of oligomannosides with different types of mannose linkages and chain lengths, which act as individual epitopes with more or less overlapping antibody specificities. Although anti-C. albicans mannan antibody levels are monitored for diagnostic purposes nothing is known about the qualitative distribution of these antibodies in terms of epitope specificity. We addressed this question using a bank of previously synthesized biotin sulfone tagged oligomannosides (BSTOs) of α and β anomery complemented with a synthetic β-mannotriose described as a protective epitope. The reactivity of these BSTOs was analyzed with IgM isotype monoclonal antibodies (MAbs) of known specificity, polyclonal sera from patients colonized or infected with C. albicans, and mannose binding lectin (MBL). Surface plasmon resonance (SPR) and multiple analyte profiling (MAP) were used. Both methods confirmed the usual reactivity of MAbs against either α or β linkages, excepted for MAb B6.1 (protective epitope) reacting with β-Man whereas the corresponding BSTO reacted with anti-α-Man. These results were confirmed in western blots with native C. albicans antigens. Using patients' sera in MAP, a significant correlation was observed between the detection of anti-mannan antibodies recognizing β- and α-Man epitopes and detection of antibodies against β-linked mannotriose suggesting that this epitope also reacts with human polyclonal antibodies of both specificities. By contrast, the reactivity of human sera with other α- and β-linked BSTOs clearly differed according to their colonized or infected status. In these cases, the establishment of an α/β ratio was extremely discriminant. Finally SPR with MBL, an important lectin of innate immunity to C. albicans, classically known to interact with α-mannose, also interacted in an unexpected way with the protective epitope. These cumulative data suggest that structure/activity investigations of the finely tuned C. albicans anti-mannose immune response are worthwhile to increase our basic knowledge and for translation in medicine. [ABSTRACT FROM AUTHOR]

We present the design and realization of a 1×4 switching matrix, based on an electro-optical directional coupler. This matrix is devoted to true time delay systems. It is characterized by an original topology that reduces global power consumption down to 20 mW. Fiber-to-fiber losses are 15 dB, and the crosstalk is lower than -20 dB. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 243–246, 1998. [ABSTRACT FROM AUTHOR]

A three-terminal edge-coupled InGaAs/InP phototransistor is reported. A dc photocurrent gain near 60 and an optical unity gain frequency of 40 GHz were measured. The mixing of a modulated optical signal and a microwave signal applied on the base terminal is presented. Optical and electrical modeling are used to analyze and improve the device performances. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 408–412, 1998. [ABSTRACT FROM AUTHOR]

A small-signal equivalent circuit model of the multielectrode lasers with saturable absorbers based on a modified formulation of the rate equations is presented. The Auger recombinations are taken into consideration because they largely modify the carrier lifetime at the high carrier densities that occur in such structures. An analysis of the bistability of the power-current characteristic is presented. The model predicts an extremely high resonance amplitude as well as a very large bandwidth up to the millimetric range, which can be very interesting for microwave optical links. The results obtained using this model are comparable to those obtained using a large-signal equivalent circuit model implanted on SPICE, the results of which are published elsewhere. The equivalent circuit obtained is a tool suitable for the study of the behavior of the multielectrode laser within a microwave optical system. [ABSTRACT FROM AUTHOR]

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 In 0.7 Ga 0.3 As 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 In 0.70 Ga 0.30 As (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 paper focuses on the simulation and optimization of electrical and structural properties. • InGaP/GaAs/Ge triple junction (3-J) solar cell incorporated by variable number of In 0.7 Ge 0.3 As. • In this goal, current density-voltage, external quantum efficiency and the capacitance-voltage. • This leads to a short-circuit current of 19.97 mA/cm2, V OC = 2.3 V, FF = 81.73%, η = 39.03%. • The C-V revealed that a relatively high number can be present in the 3-J included the QD layers. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paper compares, in terms of the error vector magnitude (EVM), the transmission of two radiocellular standards (GSM and UMTS) on two different kinds of multimode fibre (glass optical fibre and polymer optical fibre). It has been so established that the perfluorinated graded index polymer optical fibre is able to carry on wireless signals through 300-m length using standard COTS components specifically designed for glass fibre. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1197–1199, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21582 [ABSTRACT FROM AUTHOR]

A GaAsSbN layer closely lattice matched to GaAs was used as an intrinsic layer (i layer) in a GaAs/GaAsSbN/GaAs p-i-n photodiode with response up to 1.3 μm. Deep level transient spectroscopy measurement on the GaAs/GaAsSbN/GaAs reveals two types of hole traps (HTs) in the GaAsSbN i layer; (i) HT1: a shallow N-related defect state (Ea∼0.10–0.12 eV) and (ii) HT2: an AsGa point defect-related midgap defect state with Ea∼0.42–0.43 eV. Reduction in growth temperature from 480 to 420 °C reduces the HT2 trap concentration from 4×1015 to 1×1015 cm-3, while increases the HT1 trap concentration from 1×1014 to 7×1014 cm-3. Reduction in the HT2 trap concentration following growth temperature reduction was attributed to the suppression of AsGa point defect formation. Evidence of possible change of the AsGa midgap state to a shallow level defect due to the formation of (AsGa–NAs) pairs was also suggested to have increased the HT1 trap concentration and reduced the HT2 trap concentration. An ∼4 dBm improvement in photoresponse under 1.3 μm laser excitation and approximately eight times reduction in dark current at -8 V reverse bias were attributed to the reduction in the overall trap concentration and mainly the reduction of the AsGa-related midgap trap concentration in the sample grown at 420 °C. [ABSTRACT FROM AUTHOR]

A combination of a Copper Indium Gallium Selenide (CIGS) and Silicon (Si) layer has been recognized as an excellent choice for producing heterojunction based solar cells with improved efficiency and low cost processing techniques. The quaternary compound CIGS and silicon (Si) regions exhibit a lattice mismatch of about 5%, which induces a strain and impacts the electronic characteristics of the CIGS/Si heterojunction solar cell. A new viewpoint suggests the integration of a silicon germanium (Si 1-y Ge y) layer in the CIGS/Si region to reduce the impact of lattice mismatch. The objective of this study is to investigate how different gallium and germanium concentrations (x Ga and y Ge) affect the following factors: lattice mismatch (ε) , critical thickness (h c) and absorption coefficient (α)of CIGS/SiGe based solar cells. It also aims to analyze how these concentrations impact the primary parameters used to evaluate solar cell performance such as external quantum efficiency, short circuit current density, fill factor, open circuit voltage and conversion efficiency. The simulation results agree well with the existing theoretical and experimental literature data, confirming the suitability of the physical characteristics employed in this numerical study. By tuning the concentrations of Gallium and Germanium, it is feasible to attain an efficiency of 24% owing to the lattice compensation phenomenon in Si 1-y Ge y layers. These findings hold significant implications for the development and advancement of solar cell technology, as well as for enhancing their conversion efficiency and commercialization. • A strain-compensated CIGS/Si structure was achieved by adding SiGe layer. • The incorporation of SiGe improves the absorbance and EQE of the CIGS solar cell. • The improvement of the solar performances of the CIGS is ensured by the SiGe layer. • Optimizing Ga, Ge concentrations makes it possible to achieve an efficiency of 24%. [ABSTRACT FROM AUTHOR]

High-density low-loss dielectric optical interconnection is demonstrated on a monomode optical waveguide compatible with microelectronics technology. Low-loss self-aligned integrated mirrors (SAIM) on a dielectric (polyimide-silicon nitride-polyimide) optical waveguide have been fabricated. Optimization of the reactive ion etching process has been made in order to obtain vertical, homogeneous etched sidewalls. Using such a process, 45° integrated mirrors present reflection losses of 0.6 dB at a 830-nm wavelength (quasi-TE mode). [ABSTRACT FROM AUTHOR]

Abstract 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 SiO 2 /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. Highlights • The effect of AuSi LMAIS/FIB ions on nanomilling is investigated experimentally. • This effect has been shown through the study of sputtering yield. • The comparison has shown that Au+ ions are better for stable nanopatterns. • Our experimental results are in good agreement with calculated results. [ABSTRACT FROM AUTHOR]

In this work we report a modeling and optimization of a novel core (p-GaN)-multishell (i-In x Ga 1-x N/i-GaN/n-Al 0.1 Ga 0.9 N/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-In x Ga 1-x N active layer shows that x = 15% is the optimal composition that gives a good short circuit current and efficiency of about 2.24 mA/cm 2 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. [ABSTRACT FROM AUTHOR]

Aluminum doped-zinc oxide (AZO) thin films were prepared on glass substrate by radio-frequency (RF) sputtering at room temperature. The sheet resistance, R sh [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 C us is proportional to the sheet resistance R sh . 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 = C us / R sh is proportional to t 2 , which indicates that the mobility and the noise parameter α H shrink with the shrinkage of the thickness. [ABSTRACT FROM AUTHOR]

In this work we propose a modeling and simulation of core/shell p-i-n Si/Si 0.2 Ge 0.8 nanowire for photovoltaic. In the first step of this work, we have compared the core/shell p-i-n homojunction Si and heterojunction Si/Si 0.2 Ge 0.8 Nanowire (NW) solar cell having a length of 3 μm and a radius of 0.19 μm, by studying their current-voltage and external quantum efficiency (EQE). Our results have shown that blending Silicon with 80% of Germanium enhances relatively the short circuit current and efficiency by 3.04% and 8.48% respectively. In other hand, the absorption edge of Silicon NW has extended from 1100 nm to 1200 nm, with a gain of EQE of 15% obtained in this range. In the second part, we have tried to optimize the Si/Si 0.2 Ge 0.8 structure, by varying their radius and length. The corresponding results have indicated that a radius of 0.28 μm and a length of 10 μm are the optimal geometric parameters for any optimization of such structure. [ABSTRACT FROM AUTHOR]

The present study reports the impact of structural parameters on optoelectronic properties of InGasb/GaSb based quantum well structures (Qws). The laser diodes are designed to operate at 2.3 μm at 300 K. Numerical calculations of the emission wavelength, optical and modal gain of TE mode in InGaSb/GaSb laser diode structure have been carried out for various well material compositions, well thickness, number of quantum wells and temperature. The optical confinement factor and threshold current density are also simulated and reported. The calculations were performed using the 8-bands k.p model. For an injected carrier concentration of 1.56 × 1018 cm−3 at 300 K, peak gain value of the order of 1400 cm−1 is reached and a modal gain of 94 cm−1 can be obtained. A threshold current density around 3 kA/cm2, is expected to be obtained through optical losses of about 50 cm−1. The results show that InGaSb/GaSb quantum wells are appropriate for mid-infrared lasers operating at 300 K. • Type-I InGaSb/GaSb lasers, emitting at 2.3 μm are studied. • Optical/modal gain, confinement factor and the threshold current density are investigated. • A modal gain of 94 cm−1 can be reached at room temperature. • J th of 3 kA/cm2 is obtained under optical losses of about 50 cm−1 and T 0 =57 K at RT. • InGaSb/GaSb QWs are appropriate for mid-infrared lasers operating at T=300 K. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In this investigation, the mechanical properties of the different layers composing a CuIn 1 − x Ga x Se 2 (CIGS) based solar cell were studied. Magnetron sputtering technique was used for the deposition of these layers except for the cadmium sulphide (CdS) layer which was deposited using chemical bath deposition process. We performed several indentation tests on the individual layers, i.e. molybdenum (Mo) back contact layer, CIGS absorber layer, CdS and alternative zinc sulphide oxide (ZnOS) buffer layers, and zinc oxide (ZnO)-AZO (aluminium-doped zinc oxide) transparent window layer; all were deposited on glass substrates. We report the values of the hardness ( H ) and of the Young's modulus ( E ) for each material, using indentation tests and an analytical model. The Mo layer remained the hardest and the most rigid, with H = 8.7 GPa and E = 185 GPa, while the CIGS layer has shown poor mechanical properties with H = 3 GPa and E = 58 GPa. On the other hand, the observed similarity in mechanical properties of the ZnO and ZnOS layers might be attributed to the similarity of their microstructures. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A novel strategy to achieve 3D pattern transfer into silicon in a single step without using lithography is presented. Etching is performed electrochemically in HF media by contacting silicon with a positively biased, patterned, metal electrode. Dissolution is localized at the Si/metal contacts and patterning is obtained as the electrode digs into the substrate. Previous attempts at imprinting Si using bulk metal electrodes have been limited by electrolyte blockage. Here, the problem is solved by using, for the first time, a nanoporous metal electrode that allows the electrolyte to access the entire Si/metal interface, irrespective of the electrode dimensions. As a proof of concept, imprinting of well-defined arrays of inverted pyramids has been performed with sub-micrometer spatial resolution over 1 mm 2 using a nanoporous gold electrode of the complementary shape. Under a polarization of + 0.3 V/SME in 5 M HF, the etch rate is ~ 0.5 μm min − 1 . The pyramidal pattern is imprinted independently of the Si crystallographic orientation. This maskless imprinting technique opens new opportunities in the fabrication of Si microstructures. [ABSTRACT FROM AUTHOR]

In this aim, we were interested in the optimization and simulation of pin-In 1−x Ga x N 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 J sc and the maximum output power. In return, the V oc decreases consequently. For In 0.50 Ga 0.50 N structure we observed that the current density and the maximum power are respectively around 19.50 mA/cm 2 and 27.50 mW/cm 2 with a ratio of 21.65 mA/cm 2 . Also it is shown that the incorporation of the quantum well in the active region results in an increase of J sc and P max but V oc remains unchanged. The incorporation of 50 quantum well structure in the In 0.50 Ga 0.50 N gives 22 mA/cm 2 of the current density and 32 mW/cm 2 of the maximum output power. The use of the structure based on In 0.50 Ga 0.50 N (MQW) induces an efficiency of 32%. We deduced that the relative efficiency is improved by 10.9%. [ABSTRACT FROM AUTHOR]

The work reported deals with the demonstration of the use of high modal bandwidth OM4 multimode fibre as multi-purpose transmission media for short-range indoor or outdoor applications taking advantage of the wavelength division multiplexing concept. Simultaneous transmission of a digital 10GbE signal and a radio-frequency multiband orthogonal frequency division multiplexing ultra-wide band (band group 5) signal at 480 Mbits has been successfully achieved over 1.1 km fibre length without any error and with relative constellation error (RCE) less than 5.5% rms, respectively. Concerning the radio signal, an additional 1 m-long wireless path has also been demonstrated that led to an overall RCE value of 7.2%. [ABSTRACT FROM AUTHOR]

This paper proposes a method of modeling and simulation of InAs/GaAs-based quantum dots (QDs) for solar cell. The main objective is to find the growth parameters in order to produce an optimal double heterostructure using two semiconductor materials InAs and GaAs. We are interested in particular on the impact of the growth control parameters on the physical properties of the two-dimensional InAs mono-layer. We report here a complete but non-exhaustive analysis of the electronic states of the InAs based QDs layers grown on a GaAs substrate. In this work, the reader will find the modeling and the simulation results for both rectangular and elliptical geometries of InAs QDs. In the first part of this work, we provided the change of the electronic transition energy as a function of quantum dots’ radius whilst the second one concerns the absorption coefficient as a function of the incident photon wavelength. The curves we have obtained indicate clearly that the geometrical shape of the InAs QDs does significantly modify the various parameters above. We could therefore confirm that the more appropriate geometry is the elliptical one because of the higher performances. [ABSTRACT FROM AUTHOR]

Mach­Zehnder type interferometer measurements are used to determine the variation of the optical index and propagation loss. Devices are fabricated in InGaAsP/InP material line and experiments are performed at 1.3 and 1.55 μm wavelength. Combining static and dynamic measurements, the carrier life-time, the effective index and loss variation against injected current and carrier density were determined. [ABSTRACT FROM AUTHOR]

In this study, we experimentally elaborated Copper- and Indium-doped Zinc Oxide (Cu: ZnO and In: ZnO) thin films at different temperatures (T 1 = 480 °C and T 2 = 520 °C), the doping ratio were varied between 0% and 8%. Using a low cost solution-based chemical deposition, we have developed a ZnO thin film deposition process that offers fine-control of the surface morphology. It consists in spraying a volatile compound of the material to be deposited on a substrate maintained at high temperature to cause a chemical reaction in order to form at least one solid product. Therefore, the proposed ZnO doped layer is highly promising for applications for the next-generation solar cells. [ABSTRACT FROM AUTHOR]

Back-to-back GCPW-MS-GCPW (Grounded Coplanar Waveguide-Microstrip lines) transitions realized on benzocyclobutene polymer thin films (20 μm) and using copper metallization are presented in this article. The achieved experimental bandwidth is 82 GHz with a remarkably lower cutoff frequency of only 1.5 GHz and insertion loss of 0.5 dB. This performance is obtained without neither making via holes in the substrate nor patterning the bottom ground plane. These transitions make easier and faster manufacturing and characterization, by means of coplanar probes, of microwave devices realized from materials in thin film and whose driving electrode is a MS line. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2041-2045, 2015 [ABSTRACT FROM AUTHOR]

Measures the variation of propagation effective index of integrated optics devices using an heterodyne detection scheme. Direct transfer of optical phase shift in the microwave frequency range allowing phase measurements using common microwave network; Application of the technique to a digital optical switch-technique based switch.

This work reports on theoretical studies on the GaInNAs material properties (bandgap, lattice mismatch, absorption coefficient) as grown on GaAs substrate. The Band Anti-Crossing (BAC) k ⋅ p 8 × 8 model has been used to determine the influence of indium and nitrogen concentrations on the position of conduction and valence bands. The incorporation of nitrogen at a level lower than 5% causes the split of the conduction band. For indium and nitrogen concentrations of 38% and 3.5%, respectively, the strained bandgap energy is 0.70 eV and the absorption coefficient of indium and nitrogen-rich compounds increases significantly. [ABSTRACT FROM AUTHOR]

In this paper, we report a theoretical investigation of bandgap properties of GaAsNBi based materials on GaAs substrates. We look at the influence of nitrogen (N) and bismuth (Bi) concentrations on the position of conduction and valence bands; and we show that a split of the conduction band can take place with the incorporation of N at 5% under level, while a split of the valence band of both heavy and light holes sub-bands takes place after the incorporation of Bi at 14% under level. In order to compute the transition energies, we used the VBCA k.p 16×16 model. The N and Bi concentrations effects as well as the lattice mismatch value have also been taken into account. For a couple of N and Bi concentrations of 3% and 6%, we found strained gap energy around 0.68 eV. Furthermore, we have also shown that the absorption coefficient increases significantly when the N and Bi concentrations increase. [ABSTRACT FROM AUTHOR]

In this work, two process simplifications for n-type PERT (passivated emitter rear totally diffused) bifacial solar cells are investigated. Both are based on a single thermal treatment for elaborating boron and phosphorus doped regions aiming at reducing the number of high temperature steps of standard process. The first simplification shows a mixed co-diffusion from a gaseous source of phosphorus and a boron doped dielectric layer elaborated by low frequency plasma enhanced chemical vapor deposition (PECVD). The second exhibits two independent ion implantations, followed by a co-anneal/activation step. In both cases, implied open-circuit voltages are similar to standard process (~660–670 mV) and emitters allow good contacting by screen-printing ( ρ c =3.0–5.0 mΩ cm 2 ). PERT cells resulting from these processes show very promising performances with efficiency up to 19.7% on industrial 156×156 mm 2 pseudo square Cz wafers. [ABSTRACT FROM AUTHOR]

Pyramidal textures are commonly used to reduce reflections from silicon solar cells and improve light absorption by light trapping. They are generally modelled or characterised under normal incidence. In this work, a monolayer 3D ray tracing program taking into account the polarisation of light have been developed, validated and used to compute the directional-hemispherical reflectance versus the azimuth and incidence angles for both regular upright pyramids and inverted ones, with (1 1 1) facets. Results are given for a wavelength of 0.7 μ m . They show that this reflectance is not minimal at normal incidence but for an incidence angle near 20 ° and that upright pyramids can have a lower hemispherical reflectance than inverted ones for incidence angles in the middle range. The bihemispherical reflectance is 19.6% for regular upright pyramids and 20.7% for inverted ones. The effect of the pyramids aspect ratio on the hemispherical reflectance at normal incidence is also studied. This reflectance decreases with the aspect ratio of both textures. Above an aspect ratio of 0.51, inverted pyramids have a lower hemispherical reflectance. But their bihemispherical reflectance is lower only for aspect ratios below 0.23. [ABSTRACT FROM AUTHOR]

In this work, we have studied solar cells based on AlGaInAs/InP quaternary structure to describe the behavior of electronics components. To this end, we have developed a simulation program to study the gallium Ga and aluminum Al concentrations effect on respectively the lattice mismatch, the band gap energy, the absorption and the power delivered by the solar cell. This study allows us to compare between simulation and experimental results, once the cell parameters are optimized by a judicious choice of concentrations. This work allows us either to use nanotechnologies for solar cells. [ABSTRACT FROM AUTHOR]

A particular interesting plasmonic system is that of metallic nanostructures interacting with metal films. As the localized surface plasmon resonance (LSPR) behavior of gold nanostructures (Au NPs) on the top of a gold thin film is exquisitely sensitive to the spacer distance of the film-Au NPs, we investigate in the present work the influence of a few-layered graphene spacer on the LSPR behavior of the NPs. The idea is to evidence the role of few-layered graphene as one of the thinnest possible spacer. We first show that the coupling to the Au film induces a strong lowering at around 507 nm and sharpening of the main LSPR of the Au NPs. Moreover, a blue shift in the main LSP resonance of about 13 nm is observed in the presence of a few-layered graphene spacer when compared to the case where gold nanostructures are directly linked to a gold thin film. Numerical simulations suggest that this LSP mode is dipolar and that the hot spots of the electric field are pushed to the top corners of the NPs, which makes it very sensitive to surrounding medium optical index changes and thus appealing for sensing applications. A figure of merit of such a system (gold/graphene/Au NPs) is 2.8, as compared to 2.1 for gold/Au NPs. This represents a 33 % gain in sensitivity and opens-up new sensing strategies. [ABSTRACT FROM AUTHOR]

Experimental work on laser induced ablation of thin Al2O3(20 nm)/SiN:H (70 nm) and a-Si:H (20 nm)/SiN:H (70 nm) stacks acting, respectively, as p-type and n-type silicon surface passivation layers is reported. Results obtained using two different laser sources are compared. The stacks are efficiently removed using a femtosecond infra-red laser (1030 nm wavelength, 300 fs pulse duration) but the underlying silicon surface is highly damaged in a ripple-like pattern. This collateral effect is almost completely avoided using a nanosecond ultra-violet laser (248 nm wavelength, 50 ns pulse duration), however a-Si:H flakes and Al2O3 lace remain after ablation process. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work is to model the properties of GaInAsNSb/GaAs compressively strained structures. Indeed, Ga1−x In x As1−y−z N y Sb z has been found to be a potentially superior material to GaInAsN for long wavelength laser dedicated to optical fiber communications. Furthermore, this material can be grown on GaAs substrate while having a bandgap smaller than that of GaInNAs. The influence of nitrogen and antimony on the bandgap and the transition energy is explored. Also, the effect of these two elements on the optical gain and threshold current density is investigated. For example, a structure composed of one 7.5nm thick quantum well of material with In=30%, N=3.5%, Sb=1% composition exhibits a threshold current density of 339.8A/cm2 and an emission wavelength of 1.5365μm (at T=300K). It can be shown that increasing the concentration of indium to 35% with a concentration of nitrogen and antimony, of 2.5% and 1%, respectively, results in a decrease of the threshold current density down to 253.7A/cm2 for a two well structure. Same structure incorporating five wells shows a threshold current density as low as 221.4A/cm2 for T=300K, which agrees well with the reported experimental results. [Copyright &y& Elsevier]

A large majority of surface plasmon resonance (SPR) sensors reported in the literature are designed to operate in the visible electromagnetic spectrum. However, the near-infrared, particularly at the telecommunications wavelength of 1550 nm, is also especially attractive for SPR sensing applications. In fact, SPR sensors operating in this region benefit from narrower resonance and deeper field penetration. In this paper, we report a theoretical and experimental study of an SPR sensor operating at a fixed wavelength of 1550 nm. The influence of the choice of metals and the interrogation methods on the sensitivity of the resulting SPR sensor is investigated. Two types of sensor chips (simple gold (Au) and bimetallic silver/Au structure) and three interrogation methods (monitoring of the position of the reflectivity minimum, the position of the centroid, and the intensity evolution of the reflectivity) are examined. We show that a refractive index resolution of 2.7 × 10 refractive index unit can be easily obtained, and with further optimization of the measurement system, the ultimate limit of detection is expected to be even lowered. Therefore, the approach discussed here already shows a promising potential for highly sensitive SPR sensors. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) is a powerful technique for measurement of biomolecular interactions in real-time in a label-free environment. One of the most common techniques for plasmon excitation is the Kretschmann configuration, and numerous studies of ligand-analyte interactions have been performed on surfaces functionalized with a variety of biomolecules, for example DNA, RNA, glycans, proteins, and peptides. A significant limitation of SPR is that the substrate must be a thin metal film. Post-coating of the metal thin film with a thin dielectric top layer has been reported to enhance the performance of the SPR sensor, but is highly dependent on the thickness of the upper layer and its dielectric constant. Graphene is a single-atom thin planar sheet of sp2 carbon atoms perfectly arranged in a honeycomb lattice. Graphene and graphene oxide are good supports for biomolecules because of their large surface area and rich π conjugation structure, making them suitable dielectric top layers for SPR sensing. In this paper, we review some of the key issues in the development of graphene-based SPR chips. The actual challenges of using these interfaces for studying biomolecular interactions will be discussed and the first examples of the use of graphene-on-metal SPR interfaces for biological sensing will be presented. [ABSTRACT FROM AUTHOR]

Slow-wave coplanar striplines (S-CPS) have been implemented in the standard AMS 0.35 μm CMOS technology. Compared to conventional coplanar striplines (CPS), at 20 GHz, the proposed S-CPS line has more than 675% increase in quality factor, 54% improvement in the attenuation constant and 72% reduction in the electrical length. The RLCG model has also been extracted and the sources of losses have been identified. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:650-654, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26645 [ABSTRACT FROM AUTHOR]

Abstract: Surface plasmon resonance (SPR)-based biosensors are very powerful tools for the study of biomolecular interactions, chemical detection and immunoassays. This paper reviews the performance of various SPR structures and detection schemes focusing on propagating surface plasmons generated in planar structures. Some aspects of their surface functionalization, the key element which imparts biofunctionality to these structures and hence transforming them into biosensors, will also be discussed accordingly. The ultimate performance of SPR-based biosensors will thus be determined by both their inherent optical performance and suitable surface functionalization. [Copyright &y& Elsevier]

Abstract: In this paper, we provide a systematic investigation of the band alignment of quinary GaInNAsSb alloy based quantum wells, starting from the simplest ternary GaInAs compound to the new quinary GaInNAsSb one. We calculate the band gap and the band discontinuities of Ga1−x In x N y As1−y−z Sb z structures, using band anticrossing (BAC) models applied simultaneously to conduction and valence band. Nitrogen and antimony concentrations leading to an emission wavelength of 1.6μm have been determined (x=38%, y=2%, z=4%). This structure shows a good electron confinement resulting in a high characteristic temperature. GaInNAsSb has been found to be a potentially superior material to both InGaAsP and GaInNAs for communication wavelength laser applications. [ABSTRACT FROM AUTHOR]

In this paper, coplanar waveguide filters with etched-ground stubs that have multiple behaviors are proposed. The response of a unit cell is a bandreject with one or more transmission zeros according to the number and the lengths of the stubs. A library of transmission line models is being built for the basic cells and then used for the design of more elaborated structures. The potential of these new topologies is highlighted by providing different filtering structures with interesting features: a second-order narrow bandpass filter, and two configurations for a lowpass filter with a wide stopband. All theoretical predictions have been verified by electromagnetic simulation and measurements. [ABSTRACT FROM AUTHOR]

This article presents an improved factor of merit for the comparison of center-frequency tunable bandpass filters. This study draws up a comparison between existing tunable filters for which different commonly used parameters demonstrating their performance are given. A first factor of merit that takes all the major characteristics of such tunable filters into account is introduced. A second factor of merit is proposed to evaluate the filter compactness. These new factors of merit are applied for the comparison of more than 30 recently published papers. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 985–988, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24220 [ABSTRACT FROM AUTHOR]

In this article, shielded coplanar striplines (S-CPS) are studied to achieve slow-wave transmission lines in a CMOS process. The slow-wave propagation is achieved by placing floating strips below the CPS transmission line. The propagation parameters of such transmission lines are derived by simulations by means of a “full wave” 3D EM software. Quality factors as high as 35 at 10 GHz together with effective dielectric constants of 78 are reported. If these simulation results are confirmed by measurements, this would open the door to the possible realization of integrated transmission line-based RF circuits such as power dividers, phase-shifters, or filters of medium bandwidth below 10 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 352–358, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24054 [ABSTRACT FROM AUTHOR]

Abstract: The objective is to exploit the properties of the GaInNAs/GaAs alloy compressive strain structure to design a laser diode likely to meet the needs of optical communications. Modelling concerns mainly the study of the potentialities of thermal stability and dynamic response offered by these new techniques of electric and optical confinement. Band structure is modelled and typical quantum well properties are illustrated. A thorough study of the structural parameters is undertaken to take into account from the design criteria the temperature sensitivity. Minimising the Auger coefficient in the order of 10−29 cm6/s appears to allow achieving efficient laser diodes production. [Copyright &y& Elsevier]

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. • TLM samples for ρ C (e-) and ρ C (h+) measurement in SHJ cells can be fabricated while maintaining good passivation properties. • TLM measurements are carried out under illumination in order to probe ρ C (e-) and ρ C (h+) under operating conditions. • ρ C is influenced by the excess minority carrier density: it should preferably be extracted under operating conditions. • A meaningful characterization requires a good and homogeneous passivation across the TLM sample, minimal shading and low voltage bias. • Our simulations suggest a moderate impact of light on ρ C (e-) for standard c-Si doping levels. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we study the effect of the incorporation of nitrogen in strained GaInAs quantum well structures. We evaluate the influence of nitrogen on the conduction band energy by using the band anticrossing model. The incorporation of nitrogen appears to decrease the bandgap energy and increase the emission wavelength. The reduction of energy is due to the interaction of the energy of the conduction band with the level of nitrogen and more the concentration of nitrogen increases, more the energy of the band gap decreases. On the other hand, the emission wavelength increases, the advantage of the incorporation of nitrogen in such structures is to vary the wavelength between 0.980 and 1.3μm while exploiting of course the composition of gallium, composition of nitrogen and the thickness of the quantum well. Less temperature insensitive devices are so intended to be fabricated. [Copyright &y& Elsevier]