Multiphysic FEMLAB modelling to evaluate mid-infrared photonic detector performances

National audienceInfrared photo detectors operating in the mid infrared region find application in pollution monitoring, high speed infrared imaging systems and free space telecommunications. Currently the dominant infrared detector technology are based on HgCdTe or InSb photovoltaic devices. Because of their narrow band gap these devices show at room temperature (RT) high dark reverse current and small R0.A product, which significantly restrict the getting of high ambient performances. To reduce the darkness current and increase R0.A product, we suggested studying structures with large band gap energy. The objective of the photo detector structures modelling presented in this paper is double. It allows first to simulate and to estimate the theoretical performances of previously introduced large band gap components. As such we shall calculate, the product R0.A and the quantum efficiency to end in the specific detectivity D*. It is also a support to help in the understanding and in the interpretation of the made photo detectors characterizations

Artificial bee colony algorithm: a novel strategy for optical constants and thin film thickness extraction using only optical transmittance spectra for photovoltaic applications

An effective approach to determine thin film thickness (d) and optical constants (n, k, α) from transmittance spectrum with interference fringes is proposed. The developed strategy is based on applying the artificial bee colony (ABC) algorithm and Cauchy dispersion model. The accuracy test of this method has been assessed by using simulated and real tests. Simulated test is used to check the ability of ABC algorithm to determine the parameters of simulated transmittance spectra. Real test deals with the investigation of the determination approach on experimental measured transmittance spectra. Those spectra were measured from six elaborated samples of amorphous hydrogenated silicon (a-Si:H) thin films with different thicknesses, which will be used as an eco-friendly layer for solar cell applications. The obtained results noticeably show the high effectiveness of the developed strategy to accurately determine the thin film thickness and optical constants

Multiple-junction photovoltaic cell based on antimonide materials

A photovoltaic cell is provided that can be used under high levels of solar concentration (> 1000 suns). The present cell includes at least one junction produced on a Substrate based on gallium antimonide, the at least one junction having two alloys based on an antimonide material (GaAl, AsSb) lattice-matched on the substrate GaSb. If there are several junctions, two neighbouring junctions are separated by a tunnel junction

Numerical Model of Transport in Microcrystalline Silicon Films

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Croissance et propriétés des couches minces de silicium hydrogéné déposées au voisinage de la zone de transition amorphe nanocristalline par PECVD à partir d'un plasma de silane dilué dans un gaz d'argon.

L'objectif de cette thèse est de contribuer à la compréhension des propriétés optoélectroniques des couches minces de silicium hydrogénée, une étude détaillée a été effectuée. Les échantillons ont été déposés par 13,56 MHz PECVD (Plasma Enhanced Chemical Vapor Deposition) à partir du silane dilué avec l'argon (96 %). La température du substrat a été fixée à 200 C. L'influence des paramètres de dépôts sur les propriétés optiques des échantillons a été étudiée par spectroscopie UV -Vis -NIR. L'évolution structurelle a été étudiée par spectroscopie Raman, TEM, AFM, FTIR et par diffraction des rayons X (XRD). La déposition des couches intrinsèques a été faite dans cette étude dans le but d'obtenir la transition de l'état amorphe à la phase cristalline des matériaux. La pression de dépôt varie de 400 mTorr à 1400 mTorr et la puissance de 50 à 250 W. La caractérisation structurelle montre qu'au-delà de 160 W, nous avons observé une transition amorphe nanocristalline, avec une augmentation de la fraction cristalline en augmentant la puissance et la pression. Les couches sont déposées avec des vitesses de dépôt relativement élevées (3.5 - 8 Å/s), ce qui est très souhaitable pour la fabrication des cellules photovoltaïques. La vitesse de dépôt augmente avec l'augmentation de la puissance et de la pression. Des différentes fractions cristallines et tailles des cristallites ont été obtenues en contrôlant la pression et la puissance. Ces modifications de structure ont été corrélées avec la variation des propriétés optiques et électriques des couches minces déposées.The main objective of this thesis is to contribute to the understanding of the optoelectronics properties of hydrogenated nanocrystalline silicon thin films, a detailed study has been conducted. The samples were deposited by 13.56 MHz PECVD (Plasma Enhanced Chemical Vapor Deposition) of silane argon mixture. The argon dilution of silane for all samples studied was 96% by volume. The substrate temperature was fixed at 200 C. The influence of depositions parameters on optical proprieties of samples was studied by UV-Vis-NIR spectroscopy. The structural evolution was studied by Raman spectroscopy, TEM, AFM, FTIR and X-ray diffraction (XRD). Intrinsic-layer samples depositions were made in this experiment in order to obtain the transition from the amorphous to crystalline phase materials. The deposition pressure varied from 400 mTorr to 1400 mTorr and the RF power from 50 to 250 W. The structural evolution studies show that beyond 160 W, we observed an amorphous-nanocrystalline transition, with an increase in crystalline fraction by increasing RF power and working pressure. Films near the amorphous to nanocrystalline transition region are grown at reasonably high deposition rates (3.5- 8 Å/s), which are highly desirable for the fabrication of cost effective devices. The deposition rate increases with increasing RF power and process pressure. Different crystalline fractions and crystallite size can be achieved by controlling the process pressure and RF power. These structural changes are well correlated to the variation of optical and electrical proprieties of the thin films.MONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Photodétecteurs infrarouges non redroidis à superréseaux InAs/GaSb : modélisation et caractérisation optique.

Le photodétecteur à zone active constituée de superréseaux (SR) InAs/GaSb constitue l'une des filières technologiques pour la nouvelle génération de composants imageurs IR. Dans cette communication, nous présentons une modélisation des performances des photodétecteurs à SR pour un fonctionnement non refroidi, en tenant compte des caractérisations optiques effectuées sur les structures détectrices

Optical and structural proprieties of nc-Si:H prepared by argon diluted silane PECVD

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