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7 results on '"narrow band gap nanocrystals"'

1. Complex Optical Index of HgTe Nanocrystal Infrared Thin Films and Its Use for Short Wave Infrared Photodiode Design.

Author

Rastogi, Prachi, Chu, Audrey, Dang, Tung Huu, Prado, Yoann, Gréboval, Charlie, Qu, Junling, Dabard, Corentin, Khalili, Adrien, Dandeu, Erwan, Fix, Baptiste, Xu, Xiang Zhen, Ithurria, Sandrine, Vincent, Gregory, Gallas, Bruno, and Lhuillier, Emmanuel

Subjects
*THIN films, *CHARGE carrier lifetime, *NANOCRYSTALS, *SHORT films, *ELECTROMAGNETIC devices, *ELLIPSOMETRY
Abstract

The limited investigation of the optical properties of HgTe nanocrystal (NC) thin films has become a bottleneck for the electromagnetic design of devices. Using broadband ellipsometry, the refractive index (n) and the extinction coefficient (k) are determined for a series of HgTe NC films relevant to infrared sensing applications. Electromagnetic simulations reveal that the n value of HgTe NC thin films can conveniently be approximated by its mean spectral value n = 2.35 ± 0.15. This complex optical index is then used to design a diode with i) a reduced amount of Hg containing material (thin film < 150 nm) and ii) a thickness of the device better‐matched with the carrier diffusion length. It is demonstrated that introducing an aluminum grating onto the transparent conductive electrode leads to an enhanced absorption while reinforcing the work‐function difference between the two electrodes. Broadband (≈1 µm), non‐polarized, and strong absorption up to 100% is designed. This leads to a responsivity of 0.2 A W−1 and a detectivity of 2 × 1010 Jones for 2 µm cut‐off wavelength at room‐temperature, while the time response is as short as 110 ns. [ABSTRACT FROM AUTHOR]

Published
2021
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2. Electroluminescence from HgTe Nanocrystals and Its Use for Active Imaging

Author

Xavier Marie, Sandrine Ithurria, Audrey Chu, Prachi Rastogi, Corentin Dabard, Adrien Khalili, Mathieu G. Silly, Emmanuel Lhuillier, Delphine Lagarde, Junling Qu, Simon Ferré, Charlie Gréboval, Xiang Zhen Xu, Hervé Cruguel, Cedric Robert, Physico-chimie et dynamique des surfaces (INSP-E6), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de physique et chimie des nano-objets (LPCNO), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie du CNRS (INC)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut de Chimie du CNRS (INC), Laboratoire de Physique et d'Etude des Matériaux (UMR 8213) (LPEM), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), ANR-19-CE09-0026,GRaSkop,Tuning Giant Rashba Spin-Orbit Coupling in Polar Single Layer Transition Metal Dichalcogenides(2019), ANR-19-CE09-0017,FRONTAL,Nanocristaux Colloïdaux Dopés Infrarouges(2019), ANR-19-CE24-0022,COPIN,Détecteur plasmonique à nanoCristaux colloïdaux: une nouvelle filière pour l'OPtoélectronique INfrarouge(2019), ANR-18-CE30-0023,IPER-Nano2,Nanocristaux de perovskite inorganique pour la nanophotonique(2018), ANR-11-IDEX-0004,SUPER,Sorbonne Universités à Paris pour l'Enseignement et la Recherche(2011), European Project: 756225,blackQD, European Project: 853049,ne2dem, Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut de Chimie de Toulouse (ICT-FR 2599), Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut National des Sciences Appliquées (INSA)-Université de Toulouse (UT)-Institut de Chimie de Toulouse (ICT), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut National Polytechnique (Toulouse) (Toulouse INP), Université de Toulouse (UT)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Materials science, Infrared Rays, Infrared, Terahertz radiation, Bioengineering, 02 engineering and technology, Electroluminescence, HgTe, 7. Clean energy, electroluminescence, active imaging, law.invention, chemistry.chemical_compound, law, General Materials Science, Lead sulfide, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Absorption (electromagnetic radiation), Lighting, short wave infrared, narrow band gap nanocrystals, business.industry, Mechanical Engineering, Mercury telluride, [CHIM.MATE]Chemical Sciences/Material chemistry, General Chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Indium tin oxide, chemistry, Nanoparticles, Optoelectronics, Gold, Zinc Oxide, 0210 nano-technology, business, Light-emitting diode
Abstract

International audience; Mercury telluride (HgTe) nanocrystals are among of the most versatile infrared (IR) materials with the absorption of first optical absorption which can be tuned from visible to the THz range. Therefore, they have been extensively considered as near IR emitters and as absorbers for low-cost IR detectors. However, the electroluminescence of HgTe remains poorly investigated in spite of its ability to go toward longer wavelengths compared to traditional lead sulfide (PbS). Here, we demonstrate a light emitting diode (LED) based on an indium tin oxide (ITO)/zinc oxide (ZnO)/ZnO-HgTe/PbS/gold stacked structure, where the emitting layer consists of a ZnO/HgTe bulk heterojunction which drives the charge balance in the system. This LED has low turn-on voltage, long lifetime, and high brightness. Finally, we conduct short wavelength infrared (SWIR) active imaging, where illumination is obtained from a HgTe NC-based LED, and demonstrate moisture detection.

Published
2020
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3. Reconfigurable 2D/0D p-n Graphene/HgTe Nanocrystal Heterostructure for Infrared Detection

Author

Louis Donald Notemgnou Mouafo, Ulrich Nguétchuissi Noumbé, Luis E. Parra López, Audrey Chu, Clément Livache, Jean-Francois Dayen, Abdelkarim Ouerghi, Charlie Gréboval, Bernard Doudin, Hicham Majjad, Julien Chaste, Stéphane Berciaud, Emmanuel Lhuillier, chaste, julien, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Matériaux et Nanosciences Grand-Est (MNGE), Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS), Physico-chimie et dynamique des surfaces (INSP-E6), Institut des Nanosciences de Paris (INSP), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Centre de Nanosciences et de Nanotechnologies (C2N), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), lhuillier, emmanuel, Sorbonne Universités à Paris pour l'Enseignement et la Recherche - - SUPER2011 - ANR-11-IDEX-0004 - IDEX - VALID, Hétérostructures bi-dimendionnelles hybrides pour l'optoélectronique - - H2DH2015 - ANR-15-CE24-0016 - AAPG2015 - VALID, APPEL À PROJETS GÉNÉRIQUE 2018 - Nanocristaux de perovskite inorganique pour la nanophotonique - - IPER-Nano22018 - ANR-18-CE30-0023 - AAPG2018 - VALID, Détecteur plasmonique à nanoCristaux colloïdaux: une nouvelle filière pour l'OPtoélectronique INfrarouge - - COPIN2019 - ANR-19-CE24-0022 - AAPG2019 - VALID, Nanocristaux Colloïdaux Dopés Infrarouges - - FRONTAL2019 - ANR-19-CE09-0017 - AAPG2019 - VALID, Tuning Giant Rashba Spin-Orbit Coupling in Polar Single Layer Transition Metal Dichalcogenides - - GRaSkop2019 - ANR-19-CE09-0026 - AAPG2019 - VALID, ERC blackQD - blackQD - 756225 - INCOMING, ANR-11-IDEX-0004,SUPER,Sorbonne Universités à Paris pour l'Enseignement et la Recherche(2011), ANR-15-CE24-0016,H2DH,Hétérostructures bi-dimendionnelles hybrides pour l'optoélectronique(2015), ANR-18-CE30-0023,IPER-Nano2,Nanocristaux de perovskite inorganique pour la nanophotonique(2018), ANR-19-CE24-0022,COPIN,Détecteur plasmonique à nanoCristaux colloïdaux: une nouvelle filière pour l'OPtoélectronique INfrarouge(2019), ANR-19-CE09-0017,FRONTAL,Nanocristaux Colloïdaux Dopés Infrarouges(2019), ANR-19-CE09-0026,GRaSkop,Tuning Giant Rashba Spin-Orbit Coupling in Polar Single Layer Transition Metal Dichalcogenides(2019), European Project: 756225,blackQD, Université de Strasbourg (UNISTRA)-Matériaux et nanosciences d'Alsace (FMNGE), Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Réseau nanophotonique et optique, and Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)-Université de Haute-Alsace (UHA) Mulhouse - Colmar (Université de Haute-Alsace (UHA))-Centre National de la Recherche Scientifique (CNRS)-Université de Strasbourg (UNISTRA)

Subjects
Electron mobility, Materials science, General Physics and Astronomy, 02 engineering and technology, 010402 general chemistry, 7. Clean energy, 01 natural sciences, Capacitance, HgTe, law.invention, [PHYS] Physics [physics], law, General Materials Science, gate induced diode, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], narrow band gap nanocrystals, Photocurrent, [PHYS]Physics [physics], business.industry, Graphene, graphene, General Engineering, Heterojunction, infrared detection, 021001 nanoscience & nanotechnology, 0104 chemical sciences, Photodiode, Semiconductor, Optoelectronics, 0210 nano-technology, business, [PHYS.COND] Physics [physics]/Condensed Matter [cond-mat], Dark current
Abstract

International audience; Nanocrystals are promising building blocks for the development of low-cost infrared optoelectronics. Gating a nanocrystal film in a phototransistor geometry is commonly proposed as a strategy to tune the signal to noise ratio by carefully controlling the carrier density within the semiconductor. However, the performance improvement has so far been quite marginal. With metallic electrodes, the gate dependence of the photocurrent follows the gate-induced change of the dark current. Graphene presents key advantages: (i) infrared transparency that allows back-side illumination, (ii) vertical electric field transparency and (iii) carrier selectivity under gate bias. Here, we investigate a configuration of 2D/0D infrared photodetectors taking advantage of a high capacitance ionic glass gate, large scale graphene electrodes, and a HgTe nanocrystal layer of high carrier mobility. The introduction of graphene electrodes combined with ionic glass enables to reconfigure selectively the HgTe nanocrystals and the graphene electrodes between electrons (n) and holes (p) doped states. We unveil that this functionality enables to design a 2D/0D p-n junction that expands throughout the device, with a built-in electric field that assists charge dissociation. We demonstrate that in this specific configuration, the signal to noise ratio for infrared photodetection can be enhanced by two orders of magnitude, and that photovoltaic operation can be achieved. The detectivity now reaches 109 Jones while the device only absorbs 8% of the incident light. Additionally, the time response of the device is fast (

Published
2020
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4. Wavefunction engineering in HgSe/HgTe colloidal heterostructures to enhance mid infrared photoconductive properties

Author

Nicolas Goubet, Sébastien Royer, Sandrine Ithurria, Bertille Martinez, Hervé Cruguel, Xiang Zhen Xu, Emmanuel Lhuillier, Clément Livache, Mathieu G. Silly, Gilles Patriarche, Benoit Dubertret, Abdelkarim Ouerghi, Physico-chimie et dynamique des surfaces (INSP-E6), Institut des Nanosciences de Paris (INSP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et d'Etude des Matériaux (UMR 8213) (LPEM), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Centre de Nanosciences et de Nanotechnologies [Marcoussis] (C2N), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), ANR-11-IDEX-0004,SUPER,Sorbonne Universités à Paris pour l'Enseignement et la Recherche(2011), ANR-15-CE24-0016,H2DH,Hétérostructures bi-dimendionnelles hybrides pour l'optoélectronique(2015), ANR-15-CE09-0014,NanoDoSe,Dopage de Nanocristaux Semiconducteurs par chimie douce(2015), European Project: 756225,blackQD, Physico-chimie et dynamique des surfaces ( INSP-E6 ), Institut des Nanosciences de Paris ( INSP ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de Physique et d'Etude des Matériaux ( LPEM ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -ESPCI ParisTech-Centre National de la Recherche Scientifique ( CNRS ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Centre National de la Recherche Scientifique ( CNRS ), Centre de Nanosciences et de Nanotechnologies [Marcoussis] ( C2N ), Université Paris-Sud - Paris 11 ( UP11 ) -Université Paris-Saclay-Centre National de la Recherche Scientifique ( CNRS ), Synchrotron SOLEIL ( SSOLEIL ), Centre National de la Recherche Scientifique ( CNRS ), ANR-11-IDEX-0004-02/10-LABX-0067,MATISSE,MATerials, InterfaceS, Surfaces, Environment ( 2011 ), ANR : H2DH, ANR : nanodose, European Project : 756225,blackQD, and Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11)

Subjects
Materials science, nanpocrystal, Infrared spectroscopy, Bioengineering, intraband transition, 02 engineering and technology, Photodetection, 010402 general chemistry, intraband, 7. Clean energy, 01 natural sciences, Condensed Matter::Materials Science, HgSe/HgTe heterostructures, Condensed Matter::Superconductivity, General Materials Science, heterostrcture, [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], Wave function, narrow band gap nanocrystals, [PHYS]Physics [physics], [ PHYS ] Physics [physics], business.industry, Mechanical Engineering, Photoconductivity, Doping, Heterojunction, General Chemistry, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Thermal conduction, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, mid infrared, 0104 chemical sciences, Wavelength, [ CHIM.MATE ] Chemical Sciences/Material chemistry, infrared, Optoelectronics, Condensed Matter::Strongly Correlated Electrons, 0210 nano-technology, business, [ PHYS.COND ] Physics [physics]/Condensed Matter [cond-mat]
Abstract

The use of intraband transition is an interesting alternative path for the design of optically active complex colloidal materials in the mid-infrared range. However, so far, the performance obtained for photodetection based on intraband transition remains much smaller than the one relying on interband transition in narrow-band-gap materials operating at the same wavelength. New strategies have to be developed to make intraband materials more effective. Here, we propose growing a heterostructure of HgSe/HgTe as a means of achieving enhanced intraband-based photoconduction. We first tackle the synthetic challenge of growing a heterostructure on soft (Hg-based) material. The electronic spectrum of the grown heterostructure is then investigated using a combination of numerical simulation, infrared spectroscopy, transport measurement, and photoemission. We report a type-II band alignment with reduced doping compared with a core-only object and boosted hole conduction. Finally, we probe the photoconductive properties of the heterostructure while resonantly exciting the intraband transition by using a high-power-density quantum cascade laser. Compared to the previous generation of material based on core-only HgSe, the heterostructures have a lower dark current, stronger temperature dependence, faster photoresponse (with a time response below 50 μs), and detectivity increased by a factor of 30.

Published
2018
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5. Band Edge Dynamics and Multiexciton Generation in Narrow Band Gap HgTe Nanocrystals

Author

Clément Livache, Mathieu G. Silly, Sandrine Ithurria, Junling Qu, Benoit Dubertret, Nicolas Goubet, Bertille Martinez, Amardeep Jagtap, Emmanuel Lhuillier, Physico-chimie et dynamique des surfaces (INSP-E6), Institut des Nanosciences de Paris (INSP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et d'Etude des Matériaux (UMR 8213) (LPEM), Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Synchrotron SOLEIL (SSOLEIL), Centre National de la Recherche Scientifique (CNRS), Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), ANR-11-IDEX-0004,SUPER,Sorbonne Universités à Paris pour l'Enseignement et la Recherche(2011), and European Project: 756225,blackQD

Subjects
Imagination, band edge dynamics, Materials science, Chalcogenide, media_common.quotation_subject, 02 engineering and technology, Electronic structure, Photodetection, Photon energy, multi-exciton generation, 010402 general chemistry, 01 natural sciences, HgTe, chemistry.chemical_compound, General Materials Science, media_common, narrow band gap nanocrystals, photodetection, business.industry, Detector, [CHIM.MATE]Chemical Sciences/Material chemistry, 021001 nanoscience & nanotechnology, mid infrared, 0104 chemical sciences, Nanocrystal, chemistry, Excited state, [PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], Optoelectronics, 0210 nano-technology, business
Abstract

International audience; Mercury chalcogenide nanocrystals and especially HgTe appear as an interesting platform for the design of low cost mid-infrared (mid-IR) detectors. Nevertheless, their electronic structure and transport properties remain poorly understood, and some critical aspects such as the carrier relaxation dynamics at the band edge have been pushed under the rug. Some of the previous reports on dynamics are setup-limited, and all of them have been obtained using photon energy far above the band edge. These observations raise two main questions: (i) what are the carrier dynamics at the band edge and (ii) should we expect some additional effect (multiexciton generation (MEG)) as such narrow band gap materials are excited far above the band edge? To answer these questions, we developed a high-bandwidth setup that allows us to understand and compare the carrier dynamics resonantly pumped at the band edge in the mid-IR and far above the band edge. We demonstrate that fast (>50 MHz) photoresponse can be obtained even in the mid-IR and that MEG is occurring in HgTe nanocrystal arrays with a threshold around 3 times the band edge energy. Furthermore, the photoresponse can be effectively tuned in magnitude and sign using a phototransistor configuration.

Published
2018
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6. Reconfigurable 2D/0D p-n Graphene/HgTe Nanocrystal Heterostructure for Infrared Detection.

Author

Noumbé UN, Gréboval C, Livache C, Chu A, Majjad H, Parra López LE, Mouafo LDN, Doudin B, Berciaud S, Chaste J, Ouerghi A, Lhuillier E, and Dayen JF

Abstract

Nanocrystals are promising building blocks for the development of low-cost infrared optoelectronics. Gating a nanocrystal film in a phototransistor geometry is commonly proposed as a strategy to tune the signal-to-noise ratio by carefully controlling the carrier density within the semiconductor. However, the performance improvement has so far been quite marginal. With metallic electrodes, the gate dependence of the photocurrent follows the gate-induced change of the dark current. Graphene presents key advantages: (i) infrared transparency that allows back-side illumination, (ii) vertical electric field transparency, and (iii) carrier selectivity under gate bias. Here, we investigate a configuration of 2D/0D infrared photodetectors taking advantage of a high capacitance ionic glass gate, large-scale graphene electrodes, and a HgTe nanocrystals layer of high carrier mobility. The introduction of graphene electrodes combined with ionic glass enables one to reconfigure selectively the HgTe nanocrystals and the graphene electrodes between electron-doped (n) and hole-doped (p) states. We unveil that this functionality enables the design a 2D/0D p-n junction that expands throughout the device, with a built-in electric field that assists charge dissociation. We demonstrate that, in this specific configuration, the signal-to-noise ratio for infrared photodetection can be enhanced by 2 orders of magnitude, and that photovoltaic operation can be achieved. The detectivity now reaches 10 9 Jones, whereas the device only absorbs 8% of the incident light. Additionally, the time response of the device is fast (<10 μs), which strongly contrasts with the slow response commonly observed for 2D/0D mixed-dimensional heterostructures, where larger photoconduction gains come at the cost of slower response.

Published
2020
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7. Band Edge Dynamics and Multiexciton Generation in Narrow Band Gap HgTe Nanocrystals.

Author

Livache C, Goubet N, Martinez B, Jagtap A, Qu J, Ithurria S, Silly MG, Dubertret B, and Lhuillier E

Abstract

Mercury chalcogenide nanocrystals and especially HgTe appear as an interesting platform for the design of low cost mid-infrared (mid-IR) detectors. Nevertheless, their electronic structure and transport properties remain poorly understood, and some critical aspects such as the carrier relaxation dynamics at the band edge have been pushed under the rug. Some of the previous reports on dynamics are setup-limited, and all of them have been obtained using photon energy far above the band edge. These observations raise two main questions: (i) what are the carrier dynamics at the band edge and (ii) should we expect some additional effect (multiexciton generation (MEG)) as such narrow band gap materials are excited far above the band edge? To answer these questions, we developed a high-bandwidth setup that allows us to understand and compare the carrier dynamics resonantly pumped at the band edge in the mid-IR and far above the band edge. We demonstrate that fast (>50 MHz) photoresponse can be obtained even in the mid-IR and that MEG is occurring in HgTe nanocrystal arrays with a threshold around 3 times the band edge energy. Furthermore, the photoresponse can be effectively tuned in magnitude and sign using a phototransistor configuration.

Published
2018
Full Text
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