Wide and ultra-wide bandgap oxides : where paradigm-shift photovoltaics meets transparent power electronics

Oxides represent the largest family of wide bandgap (WBG) semiconductors and also offer a huge potential range of complementary magnetic and electronic properties, such as ferromagnetism, ferroelectricity, antiferroelectricity and high-temperature superconductivity. Here, we review our integration of WBG and ultra WBG semiconductor oxides into different solar cells architectures where they have the role of transparent conductive electrodes and/or barriers bringing unique functionalities into the structure such above bandgap voltages or switchable interfaces. We also give an overview of the state-of-the-art and perspectives for the emerging semiconductor β- GaO, which is widely forecast to herald the next generation of power electronic converters because of the combination of an UWBG with the capacity to conduct electricity. This opens unprecedented possibilities for the monolithic integration in solar cells of both self-powered logic and power electronics functionalities. Therefore, WBG and UWBG oxides have enormous promise to become key enabling technologies for the zero emissions smart integration of the internet of things

SYNTHÈSE ET MAÎTRISE DE LA CROISSANCE DE NANOCRISTAUX : APPLICATIONS AUX COMPOSANTS A BASE DE SEMI-CONDUCTEURS A GRANDE BANDE INTERDITE

The objective of this work was to grow, study & control the properties of ZnO thin films & nanostructures. Three growth processes were studied: Metal-Organic Chemical Vapour Deposition (MOCVD), Pulsed Laser Deposition (PLD) & Physical Vapour Transport (PVT). The substrates used were: c-Al2O3; Si, ZnO, steel, mylar & paper. The ZnO was characterized using scanning electron microscopy, photoluminescence , cathodoluminescence , X-ray diffraction & optical reflectivity. A very wide range of ZnO nanostructures was observed, including nanorods, nanoneedles, nanocombs & some novel structures. Self-forming arrays of vertically aligned nanostructures (moth-eye nanocones & nanocolumns (vertical & broadening)) could be obtained by PLD without the use of a catalyst. The various characterisation techniques indicated that these arrays were significantly better crystallized & more highly oriented than those grown by PVT/MOCVD. The feasibility of devices was also demonstrated. A nanoLED (n-nanoZnO/p-Si) had a rectifying I/V characteristic & gave blue/white electroluminescence. Moth-eye coatings on Si, resembling black-silicon, were used as templates for the growth of GaN by MOCVD. Angular-dependent specular reflection indicated that the GaN/ZnO nanostructures were broadband antireflection coatings with < 1% reflection over the visible spectrum for incidence angles < 60°. A back-gate geometry ZnO/Si3N4/SiO2/Si transparent thin film transistor was fabricated. It demonstrated a rectifying transfer characteristic, hard saturation & enhancement mode operation. Id was in the mA range & the VON was ~ 0V. Finally, conductive Amorphous Oxide Semiconductor ZnO was grown at RT on paper & mylar.Ce travail a pour objectif la maitrise de la croissance et l'analyse des propriétés des nanostructures d'oxyde de zinc (ZnO). Trois procédés de fabrication de nanostructures de ZnO ont été étudiés : dépôt chimique en phase vapeur de composés organométalliques (MOCVD), dépôt par ablation laser (PLD) et dépôt par transport physique en phase vapeur (PVT). Les substrats utilisés pour cette étude sont : saphir, silicium, ZnO massif, acier austénitique, mylar et papier. Les nanostructures ont été caractérisées par différentes techniques, notamment la microscopie électronique à balayage, la photoluminescence, la cathodoluminescence, la diffraction de rayon X et des mesures de réflectivité. Une grande variété de formes de structures a été obtenue par les trois procédés de croissance : nanofiles, nanocolonnes, nanocônes, nanopeignes. Mais par PLD on obtient des réseaux de nanocolonnes et nanocônes autoformées, alignées, verticales, homogènes dont les qualités structurales sont excellentes y compris sur des substrats avec lesquels ZnO n'a pas un bon accord paramétrique. Ces nanostructures sont obtenues sans utiliser de catalyseur. Leurs propriétés d'émission sont aussi excellentes avec des bandes de défauts, observables en PL, relativement faibles. La faisabilité de composants à base de nano ZnO a été démontrée grâce à la réalisation d'une nanoLED de type n-nanoZnO/ p-Si, mais aussi par la reprise de croissance de GaN sur des nanocônes de ZnO/Si qui agissent comme une couche antireflet (~95% d'absorption de la lumière visible). L'étude a aussi porté sur la fabrication d'un composant transistor couche mince dont les caractéristiques de transfert rectifiante ont été obtenues

Synthèse et maîtrise de la croissance de nanocristaux (applications aux composants à base de semi-conducteurs à grande bande interdite)

Ce travail a pour objectif la maitrise de la croissance et l'analyse des propriétés des nanostructures d'oxyde de zinc (ZnO). Trois procédés de fabrication de nanostructures de ZnO ont été étudiés : dépôt chimique en phase vapeur de composés organométalliques (MOCVD), dépôt par ablation laser (PLD) et dépôt par transport physique en phase vapeur (PVT). Les substrats utilisés pour cette étude sont : saphir, silicium, ZnO massif, acier austénitique, mylar et papier. Les nanostructures ont été caractérisées par différentes techniques, notamment la microscopie électronique à balayage, la photoluminescence, la cathodoluminescence, la diffraction de rayon X et des mesures de réflectivité. Une grande variété de formes de structures a été obtenue par les trois procédés de croissance : nanofiles, nanocolonnes, nanocônes, nanopeignes. Mais par PLD on obtient des réseaux de nanocolonnes et nanocônes autoformées, alignées, verticales, homogènes dont les qualités structurales sont excellentes y compris sur des substrats avec lesquels ZnO n'a pas un bon accord paramétrique. Ces nanostructures sont obtenues sans utiliser de catalyseur. Leurs propriétés d'émission sont aussi excellentes avec des bandes de défauts, observables en PL, relativement faibles. La faisabilité de composants à base de nano ZnO a été démontrée grâce à la réalisation d'une nanoLED de type n-nanoZnO/ p-Si, mais aussi par la reprise de croissance de GaN sur des nanocônes de ZnO/Si qui agissent comme une couche antireflet (~95% d'absorption de la lumière visible). L'étude a aussi porté sur la fabrication d'un composant transistor couche mince dont les caractéristiques de transfert rectifiante ont été obtenues.The objective of this work was to grow, study & control the properties of ZnO thin films & nanostructures. Three growth processes were studied: Metal-Organic Chemical Vapour Deposition (MOCVD), Pulsed Laser Deposition (PLD) & Physical Vapour Transport (PVT). The substrates used were: c-Al2O3; Si, ZnO, steel, mylar & paper. The ZnO was characterized using scanning electron microscopy, photoluminescence , cathodoluminescence , X-ray diffraction & optical reflectivity. A very wide range of ZnO nanostructures was observed, including nanorods, nanoneedles, nanocombs & some novel structures. Self-forming arrays of vertically aligned nanostructures (moth-eye nanocones & nanocolumns (vertical & broadening)) could be obtained by PLD without the use of a catalyst. The various characterisation techniques indicated that these arrays were significantly better crystallized & more highly oriented than those grown by PVT/MOCVD. The feasibility of devices was also demonstrated. A nanoLED (n-nanoZnO/p-Si) had a rectifying I/V characteristic & gave blue/white electroluminescence. Moth-eye coatings on Si, resembling black-silicon, were used as templates for the growth of GaN by MOCVD. Angular-dependent specular reflection indicated that the GaN/ZnO nanostructures were broadband antireflection coatings with < 1% reflection over the visible spectrum for incidence angles < 60. A back-gate geometry ZnO/Si3N4/SiO2/Si transparent thin film transistor was fabricated. It demonstrated a rectifying transfer characteristic, hard saturation & enhancement mode operation. Id was in the mA range & the VON was ~ 0V. Finally, conductive Amorphous Oxide Semiconductor ZnO was grown at RT on paper & mylar.PALAISEAU-Polytechnique (914772301) / SudocSudocFranceF

Study of Au coated ZnO nanoarrays for surface enhanced Raman scattering chemical sensing

International audienc

Wide and ultra-wide bandgap oxides : where paradigm-shift photovoltaics meets transparent power electronics

Oxides represent the largest family of wide bandgap (WBG) semiconductors and also offer a huge potential range of complementary magnetic and electronic properties, such as ferromagnetism, ferroelectricity, antiferroelectricity and high-temperature superconductivity. Here, we review our integration of WBG and ultra WBG semiconductor oxides into different solar cells architectures where they have the role of transparent conductive electrodes and/or barriers bringing unique functionalities into the structure such above bandgap voltages or switchable interfaces. We also give an overview of the state-of-the-art and perspectives for the emerging semiconductor β- GaO, which is widely forecast to herald the next generation of power electronic converters because of the combination of an UWBG with the capacity to conduct electricity. This opens unprecedented possibilities for the monolithic integration in solar cells of both self-powered logic and power electronics functionalities. Therefore, WBG and UWBG oxides have enormous promise to become key enabling technologies for the zero emissions smart integration of the internet of things

Preparation and Characterization of β-Ga₂O₃-based Photo detectors for UV Detection Applications

International audienceCompact photodetectors with a significant response in the UVC spectral band (100-280 nm) present a growing interest since of their potential applications to "New Space" nanosatellite constellation missions. Gallium oxide, with an already intrinsic ultra wide bandgap of 4.9 eV at 253 nm, can be engineered further into the ultraviolet (UV) by alloying it with Al. This next generation of MUV (200-300 nm) photodetectors is uniquely suitable for solar radiation from Space, and specifically the Herzberg continuum (200-242nm) that plays an important role in regional climate change through interactions with stratospheric ozone. This work presents the photolithographic, packaging and characterization of β-Ga 2 O 3-based photodetectors destined to study and improve our understanding of the solar UV impact on the Earth's climate. Different tests are used to confirm the final selection of protoflight detectors, such as photo-electric performance, photoresponse time and thermal cycle studies. These detectors are then projected to be integrated on a nanosatellite (INSPIRE-Sat 7, a "2U" cubesat) to be launched in early 2023 to monitor the absolute solar spectral irradiance and variability in the Herzberg continuum to better understand the stratospheric ozone response to solar UV irradiance changes. Results suggest that β-Ga 2 O 3-based photodetectors may certainly be a promising candidate for optoelectronic applications in the UV-detection for its high responsivity and low dark current, "solar-blindness above 250 nm" and radiation hard properties. Thermal influence, photo-responsivity and response time are reported

Performances and Calibrations of Disruptive UVC Sensors for New Space Applications

International audienceThis work overviews the development, selection and test of novel compact compact solid-state photodetectors based on β-Ga 2 O 3 , and optimized for the UVC. These sensors show inherently low dark currents, permitting room temperature operation without the need for a cooling system (mass and power savings) and thus avoiding cold surfaces trapping of environmental contamination. The oxide detectors have a spectral response peak at around 215-220 nm with a linewidth of 35 nm, providing excellent rejection of wavelengths above 250 nm ("250 nm solar-blindness"). Alloying β-Ga2O3 with Al can boost the natural bandgap of 4.9 eV up to 6 eV, thus offering deeper UV operation. Other key assets of β-Ga 2 O 3 detectors for space applications are their intrinsic radiation hardness (longer lifetime), and their high potential gain that allows operation at lower voltages (several hundreds mA/W at-5 V). Presently under characterization (on more than 100 protoflight models) and presenting very promising performances, these detectors, after calibration and selection, will be integrated on a nanosatellite (INSPIRE-Sat 7, a "2U" cubesat) to be launched in early 2023 to monitor the 200-242 nm UVC solar flux. Indeed, amongst other potential uses, these UVC Herzberg continuum detectors are a unique possibility to monitor the UV input from the Sun in the Earth's stratosphere. The sensors are also projected for use in a number of future solar and climate satellite constellation ventures

Performances and Calibrations of Disruptive UVC Sensors for New Space Applications

International audienceThis work overviews the development, selection and test of novel compact compact solid-state photodetectors based on β-Ga 2 O 3 , and optimized for the UVC. These sensors show inherently low dark currents, permitting room temperature operation without the need for a cooling system (mass and power savings) and thus avoiding cold surfaces trapping of environmental contamination. The oxide detectors have a spectral response peak at around 215-220 nm with a linewidth of 35 nm, providing excellent rejection of wavelengths above 250 nm ("250 nm solar-blindness"). Alloying β-Ga2O3 with Al can boost the natural bandgap of 4.9 eV up to 6 eV, thus offering deeper UV operation. Other key assets of β-Ga 2 O 3 detectors for space applications are their intrinsic radiation hardness (longer lifetime), and their high potential gain that allows operation at lower voltages (several hundreds mA/W at-5 V). Presently under characterization (on more than 100 protoflight models) and presenting very promising performances, these detectors, after calibration and selection, will be integrated on a nanosatellite (INSPIRE-Sat 7, a "2U" cubesat) to be launched in early 2023 to monitor the 200-242 nm UVC solar flux. Indeed, amongst other potential uses, these UVC Herzberg continuum detectors are a unique possibility to monitor the UV input from the Sun in the Earth's stratosphere. The sensors are also projected for use in a number of future solar and climate satellite constellation ventures

Preparation and Characterization of β-Ga₂O₃-based Photo detectors for UV Detection Applications

International audienceCompact photodetectors with a significant response in the UVC spectral band (100-280 nm) present a growing interest since of their potential applications to "New Space" nanosatellite constellation missions. Gallium oxide, with an already intrinsic ultra wide bandgap of 4.9 eV at 253 nm, can be engineered further into the ultraviolet (UV) by alloying it with Al. This next generation of MUV (200-300 nm) photodetectors is uniquely suitable for solar radiation from Space, and specifically the Herzberg continuum (200-242nm) that plays an important role in regional climate change through interactions with stratospheric ozone. This work presents the photolithographic, packaging and characterization of β-Ga 2 O 3-based photodetectors destined to study and improve our understanding of the solar UV impact on the Earth's climate. Different tests are used to confirm the final selection of protoflight detectors, such as photo-electric performance, photoresponse time and thermal cycle studies. These detectors are then projected to be integrated on a nanosatellite (INSPIRE-Sat 7, a "2U" cubesat) to be launched in early 2023 to monitor the absolute solar spectral irradiance and variability in the Herzberg continuum to better understand the stratospheric ozone response to solar UV irradiance changes. Results suggest that β-Ga 2 O 3-based photodetectors may certainly be a promising candidate for optoelectronic applications in the UV-detection for its high responsivity and low dark current, "solar-blindness above 250 nm" and radiation hard properties. Thermal influence, photo-responsivity and response time are reported