Integration of Emission-wavelength-controlled InAs Quantum Dots for Ultrabroadband Near-infrared Light Source

Near-infrared (NIR) light sources are widely utilized in biological and medical imaging systems owing to their long penetration depth in living tissues. In a recently developed biomedical non-invasive cross-sectional imaging system, called optical coherence tomography (OCT), a broadband spectrum is also required, because OCT is based on low coherence interferometry. To meet these operational requirements, we have developed a NIR broadband light source by integrating self-assembled InAs quantum dots (QDs) grown on a GaAs substrate (InAs/GaAs QDs) with different emission wavelengths. In this review, we introduce the developed light sources and QD growth techniques that are used to control the emission wavelength for broadband emission spectra with center wavelengths of 1.05 and 1.3 μm. Although the strain-induced Stranski-Krastanov (S-K) mode-grown InAs/GaAs QDs normally emit light at a wavelength of around 1.2 μm, the central emission wavelength can be controlled to be between 0.9–1.4 μm by the use of an In-flush technique, the insertion of a strain-reducing layer (SRL) and bi-layer QD growth techniques. These techniques are useful for applying InAs/GaAs QDs as NIR broadband light sources and are especially suitable for our proposed spectral-shape-controllable broadband NIR light source. The potential of this light source for improving the performance of OCT systems is discussed

Interdiffusion de puits quantiques induite par laser : étude de la reproductibilité et fabrication de diodes superluminescentes

Abstract : Photonic Integrated Circuits (PIC) are of tremendous interest for photonics system in order to reduce their power consumption, size, fabrication cost and improve their reliability of fiber optics linked discrete component architecture. However, unlike for microelectronics, in photonics different heterostructures are required depending on the type of device (laser sources, detectors, modulators, passive waveguides…). Therefore photonics integration needs a technology able to produce multiple bandgap energy wafers with a suitable final material quality in a reproducible manner and at a competitive cost: a technological challenge that has not been completely solved yet. Quantum Well Intermixing (QWI) is a post growth bandgap tuning process based on the localized and controlled modification of quantum well composition profile that aims to address these matters. UV laser induced QWI (UV-Laser-QWI) relies on high power excimer laser to introduce point defects near the heterostructure surface. By adjusting the laser beam shape, position, fluence and the number of pulse delivered, the different regions to be intermixed can be defined prior to a rapid thermal annealing step that will activate the point defects diffusion across the heterostructure and generate quantum well intermixing. UV-LaserQWI presents the consequent advantage of allowing the patterning of multiple bandgap regions without relying on photolithographic means, thus offering potentially larger versatility and time efficiency than other QWI processes. UV-Laser-QWI reproducibility was studied by processing samples from an InGaAs/InGaAsP/InP 5 quantum well heterostructure emitting at 1.55 µm. 217 different sites on 12 samples were processed with various laser doses. The quantum well intermixing generated was then characterized by room temperature photoluminescence (PL) mapping. Under those experimental conditions, UV-Laser-QWI was able to deliver heterostructures with a PL peak wavelength blue shift controlled within a +/- 15 % range up to 101.5nm. The annealing temperature proved to be the most critical parameter as the PL peak wavelength in the laser irradiated areas varied at the rate of 1.8 nm per degree Celsius. When processing a single wafer, thus limiting the annealing temperature variations, the bandgap tuned regions proved to be deliverable within ± 7.9%, hence establishing the potential of UV-Laser-QWI as a reproducible bandgap tuning solution. The UV-Laser-QWI was used to produce multiple bandgap wafers for the fabrication of broad spectrum superluminescent diodes (SLD). Multiple bandgap energy profiles were tested and their influence on the SLDs’ performances was measured. The most favorable bandgap modifications for the delivery of a very broadband emitting SLD were analyzed, as well as the ones to be considered for producing devices with a flat top shaped spectrum. The intermixed SLDs spectra reached full width at half maximum values of 100 nm for a relatively flattop spectrum which compare favorably with the ≈ 40nm of reference devices at equal power. The light-intensity characteristics of intermixed material made devices were very close to the ones of reference SLD made from as-grown material which let us think that the alteration of material quality by the intermixing process was extremely limited. These results demonstrated that the suitability of UV-Laser-QWI for concrete application to photonic devices fabrication. Finally, an alternative laser QWI technique was evaluated for SLD fabrication and compared to the UV laser based one. IR-RTA relies on the simultaneous use of two IR laser to anneal local region of a wafer: a 980 nm laser diode coupled to a pigtailed fiber for the wafer background heating and a 500 µm large beam TEM 00 Nd:YAG laser emitting at 1064 nm to anneal up to intermixing temperature a localized region of the wafer. The processed samples exhibited a 33 % spectral width increase of the spectrum compare to reference device at equal power of 1.5 mW. However, the PL intensity was decreased by up to 60 % in the intermixed regions and the experiments proved the difficulty to avoid these material degradations of material quality with IR-RTA.Résumé : L’intégration de circuit photonique vise à réduire la consommation énergétique, la taille, le coût et les risques de panne des systèmes photoniques traditionnels faits de composants distincts connectés par fibre optique. Cependant, contrairement à la microélectronique, des hétérostructures spécifiques sont requises pour chaque composant : lasers, détecteurs, modulateurs, guides d’ondes… De cette constatation découle le besoin d’une technologie capable de produire des gaufres d’hétérostructures III/V de qualité à plusieurs énergies de gap, et ce de façon reproductible pour un coût compétitif. Aucune des techniques actuelles ne répond pour l’instant pleinement à tous ces impératifs. L’interdiffusion de puits quantique (IPQ) est un procédé post épitaxie basé sur la modification locale de la composition des puits quantiques. L’IPQ induite par laser UV (IPQ-UV) est basée sur l’utilisation de laser excimer (Argon-Fluor émettant à 193 nm ou Krypton-Fluor à 248 nm) pour introduire des défauts ponctuels à la surface de l’hétérostructure. En ajustant la taille du faisceau, sa position, son énergie ainsi que le nombre d’impulsions laser délivrées à la surface du matériau, on peut définir les régions à interdiffuser ainsi que leur futur degré d’interdiffusion. Un recuit de la gaufre active ensuite la diffusion des défauts et par conséquent l’interdiffusion du puits. L’IPQ-UV présente l’avantage considérable de se passer de photolithographie pour définir les zones de différentes énergies de gap, diminuant ainsi la durée et potentiellement le coût du procédé. La reproductibilité de l’IPQ-UV a été étudiée pour l’interdiffusion d’une structure à 5 puits quantiques d’InGaAs/InGaAsP/InP émettant à 1.55 µm. 217 régions sur 12 échantillons ont été irradiés par un laser KrF avec des nombres d’impulsion variables selon les sites et avec une densité d’énergie constante de 155 mJ/cm². Les modifications de la structure générée par ce traitement furent ensuite mesurées par cartographie en photoluminescence (PL) à température ambiante. L’analyse des données montra que l’IPQ-UV permet un contrôle du décalage vers le bleu du pic de PL à +/- 15 % jusqu’à 101.5nm. La température du recuit est apparue comme le paramètre crucial du procédé, puisque la longueur d’onde du pic de PL des zones interdiffusées varie de 1.8 nm par degré Celsius. En considérant les sites irradiés sur une seule gaufre, c’est à dire en s’affranchissant des variations de température entre deux recuits de notre système, la variation du pic de PL est contrôlable dans une plage de ± 7.9%. Ces résultats démontrent le potentiel de l’IPQ-UV en tant que procédé reproductible de production de gaufre à plusieurs énergies de gap. L’IPQ-UV a été utilisé pour la fabrication de diodes superluminescentes (DSLs). Différents type de structure à énergie de gap multiple ont été testés et leurs influences sur les performances spectrales des diodes évalués. Les spectres des DSLs faites de matériau interdiffusé ont atteint des largeurs à mi-hauteur dépassant les 100 nm (jusqu’à 132 nm), ce qui est une amélioration conséquente des ≈ 40nm des DSLs de référence à puissance égale. Les caractéristiques intensité–courant des DSLs interdiffusés furent mesurées comme étant très proches de celle des dispositifs de référence faits de matériau brut, ce qui suggère que l’IPQ-UV n’a pas ou très peu altéré la qualité du matériau initial. Ces résultats prouvent la capacité de l’IPQ-UV à être utilisé pour la fabrication de dispositifs photoniques. Une technique alternative d’IPQ par laser a été évaluée et comparée à l’IPQ-UV pour la fabrication de DSL. Le recuit rapide par laser IR est basé sur l’utilisation simultanée de deux lasers IR pour chauffer localement l’hétérostructure jusqu’à une température suffisante pour provoquer l’interdiffusion: une diode laser haute puissante émettant à 980 nanomètre couplée dans une fibre chauffe la face arrière de la gaufre sur une large surface à une température restant inférieure à celle requise pour provoquer l’interdiffusion et un laser Nd:YAG TEM 00 émettant à 1064 nm un faisceau de 500 µm de large provoque une élévation de température additionnelle localisée à la surface de l’échantillon, permettant ainsi l’interdiffusion de l’hétérostructure. Les dispositifs fabriqués ont montré une augmentation de 33 % de la largeur à mi-hauteur du spectre émis à puissance égale de 1.5 mW. Cependant, l’intensité du pic de PL dans les zones interdiffusées est diminuée de 60 %, suggérant une dégradation du matériau et la difficulté à produire un matériau de qualité satisfaisante

Strain-Tuning of the Optical Properties of Semiconductor Nanomaterials by Integration onto Piezoelectric Actuators

The tailoring of the physical properties of semiconductor nanomaterials by strain has been gaining increasing attention over the last years for a wide range of applications such as electronics, optoelectronics and photonics. The ability to introduce deliberate strain fields with controlled magnitude and in a reversible manner is essential for fundamental studies of novel materials and may lead to the realization of advanced multi-functional devices. A prominent approach consists in the integration of active nanomaterials, in thin epitaxial films or embedded within carrier nanomembranes, onto Pb(Mg1/3Nb2/3)O3-PbTiO3-based piezoelectric actuators, which convert electrical signals into mechanical deformation (strain). In this review, we mainly focus on recent advances in strain-tunable properties of self-assembled InAs quantum dots embedded in semiconductor nanomembranes and photonic structures. Additionally, recent works on other nanomaterials like rare-earth and metal-ion doped thin films, graphene and MoS2 or WSe2 semiconductor two-dimensional materials are also reviewed. For the sake of completeness, a comprehensive comparison between different procedures employed throughout the literature to fabricate such hybrid piezoelectric-semiconductor devices is presented. Very recently, a novel class of micro-machined piezoelectric actuators have been demonstrated for a full control of in-plane stress fields in nanomembranes, which enables producing energy-tunable sources of polarization-entangled photons in arbitrary quantum dots. Future research directions and prospects are discussed.Comment: review manuscript, 78 pages, 27 figure

Quantum dots for photonic quantum information technology

The generation, manipulation, storage, and detection of single photons play a central role in emerging photonic quantum information technology. Individual photons serve as flying qubits and transmit the quantum information at high speed and with low losses, for example between individual nodes of quantum networks. Due to the laws of quantum mechanics, quantum communication is fundamentally tap-proof, which explains the enormous interest in this modern information technology. On the other hand, stationary qubits or photonic states in quantum computers can potentially lead to enormous increases in performance through parallel data processing, to outperform classical computers in specific tasks when quantum advantage is achieved. Here, we discuss in depth the great potential of quantum dots (QDs) in photonic quantum information technology. In this context, QDs form a key resource for the implementation of quantum communication networks and photonic quantum computers because they can generate single photons on-demand. Moreover, QDs are compatible with the mature semiconductor technology, so that they can be integrated comparatively easily into nanophotonic structures, which form the basis for quantum light sources and integrated photonic quantum circuits. After a thematic introduction, we present modern numerical methods and theoretical approaches to device design and the physical description of quantum dot devices. We then present modern methods and technical solutions for the epitaxial growth and for the deterministic nanoprocessing of quantum devices based on QDs. Furthermore, we present the most promising concepts for quantum light sources and photonic quantum circuits that include single QDs as active elements and discuss applications of these novel devices in photonic quantum information technology. We close with an overview of open issues and an outlook on future developments.Comment: Copyright 2023 Optica Publishing Group. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibite

개별 어드레싱이 가능한 복합차원 나노소자 어레이

학위논문 (박사)-- 서울대학교 대학원 : 자연과학대학 물리·천문학부, 2018. 2. 이규철.One-dimensional (1D) semiconductor nanomaterial arrays grown on two-dimensional (2D) layered nanomaterials can provide an excellent platform for realizing novel electronic and optoelectronic devices by synergistically combining the unique physical properties of 1D and 2D nanomaterials. 1D semiconductor nanomaterials work as efficient channels for carrier transport, thereby greatly improving the device performances of electronic and optoelectronic devices. Moreover, graphene layers, which have excellent electrical and thermal conductivities, and high mechanical strength and elasticity, are novel substrates that offer new functionalities such as transferability and flexibility. This dissertation presents the fabrication and characteristics of individually addressable nanorod device arrays based on 1D+2D hybrid dimensional nanomaterials. Ultrathin, flexible, and individually addressable ZnO nanorod device arrays on graphene layers were demonstrated. Using this system, we investigated the individual electrical characteristics of single ZnO nanorod within the arrays. Additionally, based on the optoelectronic and piezoelectronic characteristics of ZnO nanorods, we investigated photodetector and pressure sensor characteristics of the nanorod device arrays. Moreover, light-emitting diode (LED) arrays were fabricated using GaN/ZnO coaxial nanorod heterostructure arrays and their device characteristics were investigated. Metal-cored nitride microtube structures are discussed as a method to significantly improve nanostructured LED performance by improving the current-spreading characteristics. In addition to 1D+2D hybrid dimensional nanomaterial-based devices, semiconductor microstructure arrays grown on graphene substrates were used to show their potential for microdisplay. GaN microdisk LED arrays grown on graphene dots were assembled in ultrathin and individually addressable crossbar array for flexible, high-resolution microdisplay. Furthermore, for full-color microdisplay, morphology-controlled GaN microdonut-shaped and micropyramidal LEDs were used to demonstrate variable-color light-emitters. The interesting electrical and electroluminescence characteristics of the GaN nanoarchitecture LEDs are presented. The origin of multicolor emission is also investigated by analysing the structure and chemical composition of the LEDs by TEM. The catalyst-free molecular beam epitaxy (MBE) growth of InxGa1−xAs/InAs coaxial nanorod heterostructures on graphene layers are also demonstrated. Transmission electron microscopy (TEM) was used to investigate the crystallinity of the arsenide nanorods grown on graphene layers. Additionally, RHEED was used to investigate the growth behavior of nanorods on graphene layers in real time. Finally, monolithic integration of wide and narrow band gap semiconductor nanorods vertically on each surface of graphene are demonstrated by showing InAs nanorods/graphene layers/ZnO nanorods double heterostructures. Their structural characteristics are investigated by both the cross-sectional and plan view TEM. Moreover, their dual-wavelength photodetector characteristics are demonstrated.Chapter 1. Introduction 1 1.1. Hybrid dimensional nanomaterials and nanodevices 1 1.2. Objective and approach 2 1.3. Outline 3 Chapter 2. Background and literature survey 5 2.1. Nanodevices made of 1D semiconductor nanomaterials assembly 5 2.2.1. Horizontally assembled 1D nanomaterial-based devices 5 2.2.2. Vertically aligned 1D nanomaterial-based devices 7 2.2. Semiconductor nano- and micro-structure devices on graphen substrates 11 2.3. Ultrathin and flexible devices 15 Chapter 3. Experimental methods 18 3.1. Growth of semiconductor nanostructures on graphene substrates 18 3.1.1. Preparation of graphene substrates 18 3.1.2. Selective-area metal-organic vapor-phase epitaxy of ZnO and GaN semiconductors 19 3.1.3. Catalyst-free molecular beam epitaxy of InxGa1xAs/InAs coaxial nanorod heterostructures on graphene layers 22 3.2. Fabrication of ultrathin and individually addressable nanorod device arrays 24 3.2.1. Preparation of ultrathin layers composed of nanorod arrays on graphene layers 24 3.2.2. Microelectrodes formation on ultrathin layers 25 3.3. Fabrication of nanoarchitecture light-emitting diodes 26 3.3.1. GaN micropyramid and microdonut LED fabrication 26 3.3.2. Metal-cored GaN microtube LED fabrication 27 3.4. Fabrication of ultrathin microdisplay using GaN microdisks grown on graphene dots 28 3.4.1. Transfer and assembly of microdisk LEDs in ultrathin form 28 3.4.2. Single walled carbon nanotubes (SWCNT) embedded metal microelectrodes 31 3.5. Electrical and optical characterization 32 3.4.1. Electrical characterizations of individually addressable nanorod device arrays 32 3.4.2. Photodetector characterizations 33 3.4.3. Pressure sensor characterizations 34 3.4.4. LED characterizations 36 3.6. Structural characterization 37 Chapter 4. Individually addressable nanorod device arrays on graphene substrate 38 4.1. Introduction 38 4.2. Ultrathin and individually addressable ZnO nanorod device arrays on graphene layers 40 4.2.1. Electrical characteristics of individual ZnO nanorod devices 45 4.2.2. Flexible device characteristics 48 4.3. High-spatial-resolution ZnO photodetector arrays on graphene 51 4.3.1. Photodetector characteristics of ZnO nanorod devices 51 4.3.2. Spectral and temporal responses 52 4.4. High-spatial-resolution ZnO nanorod pressure sensor arrays on graphene 54 4.5. Light-emitting diodes using GaN/ZnO coaxial nanorod arrays 57 4.5.1. GaN/ZnO coaxial nanorod LED arrays on graphene 58 4.5.2. Metal-cored nitride semiconductor microtube LED arrays 62 4.6. Summary 77 Chapter 5. Microstructure light-emitting diode arrays on graphene substrates for display applications 79 5.1. Introduction 79 5.2. GaN microdisk light-emitting diode display fabricated on graphene 80 5.3.1. Device structure 81 5.3.2. Device characteristics of individually addressable GaN microdisk LEDs 83 5.3. Morphology-controlled GaN nanoarchitecture LED arrays for full-color microdisplay applications 89 5.2.1. Monolithic multicolor GaN micropyramid LED array 89 5.2.2. Variable color GaN microdonut LED array 100 5.4. Summary 110 Chapter 6. Concluding remarks and outlooks 111 6.1. Summary 111 6.2. Suggestions for future works 11 Appendix A. Molecular beam epitaxy of arsenide semiconductor nanorods on graphene 113 A.1. Introduction 113 A.2. Catalyst-free molecular beam epitaxy (MBE) of III-As coaxial semiconductor nanorod heterostructures on graphene 114 A.2.1. Growth method and general morphology of InAs/InxGa1xAs nanorods on graphene 114 A.2.2. Effect of growth temperature 118 A.2.3. Effect of beam equivalent fluxes 119 A.3. In-situ characterization using reflection high energy electron diffraction (RHEED) 122 A.4. Ex-situ characterization using transmission electron microscopy (TEM) 126 Appendix B. Monolithic integration of wide and narrow band gap semiconductor nanorods on graphene substrate 133 B.1. Introduction 133 B.2. ZnO nanorods/graphene layers/InAs nanorods heterostructures 134 B.2.1. Growth and structural characteristics 134 B.2.2. Dual wavelength photodetector device characteristics 143 B.3. Summary 145 References 146 Abstract in Korean 157 Curriculum Vitae 160Docto

Fingerprints in the Optical and Transport Properties of Quantum Dots

The book "Fingerprints in the optical and transport properties of quantum dots" provides novel and efficient methods for the calculation and investigating of the optical and transport properties of quantum dot systems. This book is divided into two sections. In section 1 includes ten chapters where novel optical properties are discussed. In section 2 involve eight chapters that investigate and model the most important effects of transport and electronics properties of quantum dot systems This is a collaborative book sharing and providing fundamental research such as the one conducted in Physics, Chemistry, Material Science, with a base text that could serve as a reference in research by presenting up-to-date research work on the field of quantum dot systems

Cutting Edge Nanotechnology

The main purpose of this book is to describe important issues in various types of devices ranging from conventional transistors (opening chapters of the book) to molecular electronic devices whose fabrication and operation is discussed in the last few chapters of the book. As such, this book can serve as a guide for identifications of important areas of research in micro, nano and molecular electronics. We deeply acknowledge valuable contributions that each of the authors made in writing these excellent chapters

Ultrafast nonlinear silicon waveguides and quantum dot semiconductor optical amplifiers

In this book, nonlinear silicon-organic hybrid waveguides and quantum dot semiconductor optical amplifiers are investigated. Advantageous applications are identified, and corresponding proof-of-principle experiments are performed. Highly nonlinear silicon-organic hybrid waveguides show potential for all-optical signal processing based on fourwave mixing and cross-phase modulation. Quantum dot semiconductor optical amplifiers operate as linear amplifiers with a very large dynamic range

Mécanismes fondamentaux et dynamique d'interdiffusion dans les boîtes quantiques auto-assemblées INAS/INP

Généralités sur les BQ InAs/InP -- Principes physiques et techniques d'interdiffusion -- État des structures après croissance et influence du recuit conventionnel -- Interdiffusion assistée par les défauts de croissance -- Interdiffusion assistée par implantation ionique