Fabrication and electro-optical characterization of InAs/GaSb superlattices infrared photodetectors

Ce manuscrit de thèse porte sur l'étude et la réalisation de photodétecteurs infrarouges à superréseaux (SR), constitués d'hétérostructures de semiconducteurs InAs/GaSb. Ces superréseaux InAs/GaSb sont considérés, depuis le milieu des années 2000, comme des structures pouvant satisfaire les besoins de la prochaine génération de photodétecteurs infrarouges (IR). À l'Institut d'Electronique du Sud (IES) de l'Université Montpellier 2, nous maîtrisons la réalisation des structures périodiques à SR par Epitaxie par Jets Moléculaires sur substrat GaSb et la fabrication technologique des photodiodes pin. Ces composants présentent des performances à l'état de l'art mondial dans le MWIR.L'objectif de mon travail de thèse, financé par la DGA et en collaboration étroite avec l'ONERA, était de contribuer à une meilleure compréhension de la physique du composant et d'améliorer les performances de cette nouvelle filière de détecteur IR. Cette étude s'effectua sur des monoélements (pixels), éléments de base du système imageur IR. En comparant trois structures InAs/GaSb différentes, conçus pour la même gamme spectrale de détection dans le MWIR mais de composition et d'épaisseur différentes (riche en GaSb, symétrique et riche en InAs), nous avons exploité la flexibilité offerte par cette technologie de détecteurs. Cette approche nous a permis de mettre en évidence la dépendance des performances avec la proportion en GaSb. Les résultats obtenus sur les structures asymétriques plus riches en InAs sont à l'état de l'art pour des photodiodes : densité de courant d'obscurité de 5x 10-8 A/cm2 à 77K pour une polarisation inverse de 50 mV. En complément, nous avons réalisé, en collaboration avec le CEA-LETI, la première matrice à SR française. Ces résultats ont contribué à une meilleure compréhension des détecteurs à superréseaux et esquissent des voies d'optimisation prometteuses.This thesis focuses on the study and implementation of infrared photodetectors with InAs/GaSb superlattices (SL). Since the mid-2000s, InAs/GaSb SL are considered as new technology that can meet the criteria of the next generation of infrared (IR) photodetectors. At the Institut d'Electronique du Sud (IES) of the University of Montpellier 2, we control the fabrication of SL periodic structures by Molecular Beam Epitaxy on GaSb substrate and the technological process of pin photodiodes. These devices have performances at the state of the art in the midwave infrared spectral domain.The aim of my thesis work, funded by the DGA and in close collaboration with ONERA, was to contribute to a better understanding of the device physics and improve the performance of this IR detector. This study was carried out on mono-element (pixel), the basic elements of IR imaging system. Comparing three different InAs/GaSb structures, designed for the same detection spectral range (MWIR) but different composition and thickness (GaSb-rich, symmetric and InAs-rich), we used the flexibility offered by this technology detectors. This approach has allowed us to highlight the dependence of performances with the proportion on GaSb in the SL structure. The results obtained on InAs-rich asymmetric photodiodes are at the state of the art: dark current density of 5×10-8 A/cm2 at 77K for a reverse bias of 50 mV. In addition, the first French SL Focal Plane Array has been fabricated and tested. These results contributed to a better understanding of superlattice detectors and outline ways of promising optimization

Influence of the period thickness and composition on the electro-optical properties of type-II InAs/GaSb midwave infrared superlattice photodetectors

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Comparison of the electro-optical performances of symmetrical and asymmetrical MWIR InAs/GaSb superlattice pin photodiodes

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Noise performance analysis of MWIR InAs/GaSb superlattice pin photodiodes

International audienceWe report the full electrooptical characterization of a MWIR InAs/GaSb superlattice (SL) pin photodiode, including dark current, noise, spectral response and quantum efficiency measurements. The SL structure was made of 8 InAs monolayers (MLs) and 8 GaSb MLs, with a total thickness of 3 mu m. It exhibits a cut-off wavelength of 4.55 mu m at 77K. Dark current measurements reveal a diffusion-limited behavior for temperatures higher than 95K, and a R0A value of 1x10(6)Omega.cm(2) at 77K. Noise measurements were performed under dark conditions and are interpreted in this paper. The results show that the SL detector remains Schottky noise-limited up to a bias voltage of -600mV and that 1/f noise is not present above 6Hz. Spectral response revealed that the cut-off wavelength increases from 4.48 mu m to 4.91 mu m when the temperature increases from 12K to 170K. The quantum efficiency in photovoltaic mode and at 77K is 25% (3 mu m-thick active zone device, single pass and without any antireflection coating). All these electrooptical performances confirm the high quality of the MWIR SL pin photodiode under test

Comparison of the electro-optical performances of MWIR InAs/GaSb superlattice pin photodiode and FPA with asymmetrical designs

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Performances Analysis of Symmetrical and Asymmetrical InAs/GaSb Superlattice pin Photodiode

International audienceSymmetric and asymmetric mid-wavelength infrared (MWIR) InAs/GaSb superlattice (SL) pin photodiode were fabricated by Molecular Beam Epitaxy (MBE) on p-type GaSb substrate and characterized as a function of temperature. The symmetric SL structure was made of 8 InAs monolayers (MLs) and 8 GaSb MLs and exhibits at 80K a cut-off wavelength (lambda c) of 4.5 mu m, while the asymmetric SL design was composed of 7.5 InAs MLs and 3.5 GaSb MLs for lambda c = 5.5 mu m at 80K. Optical characterizations made of photoluminescence as a function of temperature and room temperature absorption spectra were performed on these two kinds of structures. Several electrical characterizations including dark current and capacitance-voltage measurements were also carried out on single detectors in the temperature range [77K-300K]. Results obtained were compared and analyzed in order to define optimized SL structure design for the high performance in the MWIR domain