Добірка наукової літератури з теми "Nonpolar III-Nitrides"

In the last two decades, the third-generation wide bandgap semiconductor III-nitrides have revolutionized a myriad of electronic and photonic devices and applications, including power electronics, extreme-environment electronics, RF amplifiers, and optoelectronics such as light-emitting diodes and laser diodes. Recently, III-nitride heterostructures (e.g., AlGaN/GaN) based intersubband transition (ISBT) has garnered considerable research interest for infrared (IR), terahertz (THz), and ultrafast optoelectronics (e.g., photodetectors and quantum cascade lasers) due to its large conduction band offset, large optical phonon energy, and promising room-temperature operation. This paper presents a comprehensive review on the recent progress and challenges of III-nitrides based ISBT from the perspectives of materials, structures, devices, and applications, with a focus on nonpolar and semipolar III-nitrides. Various device structures have been demonstrated for III-nitrides based ISBT, including quantum wells, dots, and wires, among which AlGaN/GaN quantum wells are the most widely used. The effects of device parameters, crystal orientations, and doping on the ISBT properties of AlGaN/GaN quantum wells are discussed. Although the room-temperature operation is still elusive, theoretical and experimental studies show that nonpolar and semipolar III-nitrides based ISBT exhibits tunable ISBT wavelength from far-IR to THz spectral range with higher efficiency compared with polar c-plane ISBT. This review can serve as a gateway to and an important reference for the recent progress and challenges of III-nitrides based ISBT and its potential applications in sensing, communication, ultrafast optoelectronics, and integrated photonics.

A simplified model of the process is considered nucleation of defects for optimization of template layers of nanostructures with three-dimensional restrictions When using optimized porous anode template layers aluminum oxide formed on Si (100) substrate, a nitride layer was grown by the chloride-hydride gas-phase epitaxy method gallium, which turned out to be nonpolar with (11 2 0) α- orientation and low anisotropy. Spectra micro cathodoluminescence of the grown films confirms the low density of packing defects

Light-emitting diodes (LEDs) based on group III-nitride semiconductors (GaN, AlN, and InN) are crucial elements for solid-state lighting and visible light communication applications. The most widely used growth plane for group III-nitride LEDs is the polar plane (c-plane), which is characterized by the presence of a polarization-induced internal electric field in heterostructures. It is possible to address long-standing problems in group III-nitride LEDs, by using semipolar and nonpolar orientations of GaN. In addition to the reduction in the polarization-induced internal electric field, semipolar orientations potentially offer the possibility of higher indium incorporation, which is necessary for the emission of light in the visible range. This is the preferred growth orientation for green/yellow LEDs and lasers. The important properties such as high output power, narrow emission linewidth, robust temperature dependence, large optical polarization ratio, and low-efficiency droop are demonstrated with semipolar LEDs. To harness the advantages of semipolar orientations, comprehensive studies are required. This review presents the recent progress on the development of semipolar InGaN/GaN quantum well LEDs. Semipolar InGaN LED structures on bulk GaN substrates, sapphire substrates, free-standing GaN templates, and on Silicon substrates are discussed including the bright prospects of group III-nitrides. Keywords: Group III-nitride semiconductor, semipolar, light-emitting diodes, InGaN/GaN quantum well.

High efficiency artificial photosynthesis, that can convert solar energy directly into chemical fuels, has been extensively investigated. To date, however, success in finding abundant visible-light active photocatalyst has been very limited. Recently, metal-nitrides (e.g. InGaN) have attracted considerable attention for applications in artificial photosynthesis, due to their excellent stability and tunable energy bandgap across nearly the entire solar spectrum. Moreover, InGaN is the only known material whose energy bandgap can straddle the redox potential of water under deep visible and near-infrared light irradiation. In this context, we have investigated the design, fabrication, and performance characterization of multi-band InGaN/GaN nanowire photocatalysts and photoelectrodes for solar water splitting and carbon dioxide reduction. In this work, InGaN nanowires are grown on Si substrate by molecular beam epitaxy. The water splitting reaction takes place on the nonpolar surface (m-planes) of InGaN nanowire photocatalysts. By optimizing the surface charge properties through controlled Mg dopant incorporation, the efficiency for solar-to-hydrogen conversion is enhanced by nearly two orders of magnitude. The absorbed photon conversion efficiency reaches ~90% with optimum Mg doping concentration. The significantly enhanced efficiency is directly related to the optimized surface electronic properties that lead to both efficient water oxidation and proton reduction. A solar-to-hydrogen conversion efficiency of 3.3% and stability >500 hours was demonstrated in photocatalytic overall water splitting. High stability of these nanowires is attributed to the N-rich surfaces of GaN nanowire structures, which protects against photocorrosion and oxidation. We have further demonstrated multi-band InGaN/GaN nanowire photoelectrodes monolithically integrated on a Si solar cell wafer. The tandem PEC device consists of a planar n+-p Si solar cell wafer and p-InGaN nanowire segments. The p-InGaN nanowire arrays are designed to absorb the ultraviolet and visible solar spectrum. The remaining photons with wavelengths up to 1.1 µm are absorbed by the underlying planar Si p-n junction. Such a monolithically integrated photocathode promises solar-to-hydrogen conversion efficiency >20%. With the use of such a photoelectrode, we have also demonstrated that syngas, a key feedstock to produce methanol and liquid fuels in industry, can be produced from a CO2 and H2O with a benchmark turnover number of 1330 and a desirable CO/H2 ratio of 1:2. Work is currently in progress to achieve high efficiency syngas and methanol generation in an aqueous photoelectrochemical cell.

The popularity of III-nitride materials has taken up the semiconductor industry to newer applications because of their remarkable properties. In addition to having a direct and wide band gap of 3.4 eV, a very fascinating property of GaN is the band gap tuning from 0.7 to 6.2 eV by alloying with Al or In. The most common orientation to grow optoelectronic devices out of these materials are the polar c-plane which are strongly affected by the intrinsic spontaneous and piezoelectric polarization fields. Devices grown in no polar orientation such as (1 0 –1 0) m-plane or (1 1 –2 0) a-plane have no polarization in the growth direction and are receiving a lot of focus due to enhanced behaviour. The first part of this thesis deals with the development of non-polar epimGaN films of usable quality, on an m-plane sapphire by plasma assisted molecular beam epitaxy. Growth conditions such as growth temperature and Ga/N flux ratio were tuned to obtain a reasonably good crystalline quality film. MSM photodetectors were fabricated from (1 0 -1 0) m-GaN, (1 1 -2 0) a-GaN and semipolar (1 1 -2 2) GaN films and were compared with the polar (0 0 0 2) c-GaN epilayer. Later part of the thesis investigated (1 0 -1 0) InN/ (1 0 -1 0) GaN heterostructures. Further, we could successfully grow single composition nonpolar a-plane InxGa1-xN epilayers on (1 1 -2 0) GaN / (1 -1 0 2) sapphire substrate. This thesis focuses on the growth and characterisation of nonpolar GaN, InxGa1-xN and InN by plasma assisted molecular beam epitaxy and on their photodetection potential. Chapter 1 explains the motivation of this thesis work with an introduction to the III-nitride material and the choice of the substrate made. Polarization effect in the polar, nonpolar and semipolar oriented growth is discussed. Fabrication of semiconductor photodetectors and its principle is explained in details. Chapter 2 discusses the various experimental tools used for the growth and characterisation of the film. Molecular beam epitaxy technique is elaborately explained along with details of the calibration for the BEP of various effusion cells along with growth temperature at the substrate. Chapter 3 discusses the consequence of nitridation on bare m-sapphire substrate. Impact of nitridation step prior to the growth of GaN film over (1 0 -1 0) m-sapphire substrate was also studied. The films grown on the nitridated surface resulted in a nonpolar (1 0 -1 0) orientation while without nitridation caused a semipolar (1 1 -2 2) orientation. Room temperature photoluminescence study showed that nonpolar GaN films have higher value of compressive strain as compared to semipolar GaN films, which was further confirmed by room temperature Raman spectroscopy. The room temperature UV photodetection of both films was investigated by measuring the I-V characteristics under UV light illumination. UV photodetectors fabricated on nonpolar GaN showed better characteristics, including higher external quantum efficiency, compared to photodetectors fabricated on semipolar GaN. Chapter 4 focuses on the optimization and characterisation of nonpolar (1 0 -1 0) m-GaN on m-sapphire by molecular beam epitaxy. A brief introduction to the challenges in growing a pure single phase nonpolar (1 0 -1 0) GaN on (1 0 -1 0) sapphire without any other semipolar GaN growth is followed by our results achieving the same. Effect of the growth temperature and Ga/N ratio on the structural and optical properties of m-GaN epilayers was studied and the best condition was obtained for the growth temperature of 7600C and nitrogen flow of 1 sccm. Strain in the film was quantitatively measured using Raman spectroscopy and qualitatively analyzed by RSM. Au/ nonpolar GaN schottky diode was fabricated and temperature dependent I-V characteristics showed rectifying nature. Chapter 5 demonstrates the growth of (1 0 -1 0) m-InN / (1 0 -1 0) m-GaN / (1 0 -1 0) m-sapphire substrate. Nonpolar InN layer was grown at growth temperature ranging from 3900C to 440C to obtain a good quality film at 4000C. An in-plane relationship was established for the hetrostructures using phi-scan and a perfect alignment was found for the epilayers. RSM images on the asymmetric plane revealed highly strained layers. InN band gap was found to be around 0.8 eV from absorption spectra. The valance band offset value is calculated to be 0.93 eV for nonpolar m-plane InN/GaN heterojunctions. The heterojunctions form in the type-I straddling configuration with a conduction band offsets of 1.82 eV. Chapter 6 focuses on the optimization of nonpolar (1 1 -2 0) a-GaN on (1 -1 0 2) r-sapphire by molecular beam epitaxy. Effect of the growth temperature and Ga/N ratio on the structural and optical properties of a-GaN epilayers was studied and the best condition was obtained for the growth temperature of 7600C and nitrogen flow of 1 sccm. An in-plane orientation relationship is found to be [0 0 0 1] GaN || [-1 1 0 1] sapphire and [-1 1 0 0] GaN || [1 1 -2 0] sapphire for nonpolar GaN on r-sapphire substrate. Strain in the film was quantitatively measured using Raman spectroscopy and qualitatively analyzed by RSM. UV photo response of a-GaN film was measured after fabricating an MSM structure over the film with Au. EQE of the photodetectors fabricated in the (0 0 0 2) polar and (1 1 -2 0) nonpolar growth directions were compared in terms of responsively, nonpolar a-GaN showed the best sensitivity at the cost of comparatively slow response time. Chapter 7 demonstrates the growth of non-polar (1 1 -2 0) a-plane InGaN epilayers on a-plane (1 1 -2 0) GaN/ (1 -1 0 2) r-plane sapphire substrate using PAMBE. The high resolution X-ray diffraction (HRXRD) studies confirmed the orientation of the films and the compositions to be In0.19Ga0.81N, In0.21Ga0.79N and In0.23Ga0.77N. The compositions of the films were controlled by the growth parameters such as growth temperature and indium flux. Effect of variation of Indium composition on the strain of the epilayers was analyzed from the asymmetric RSM images. Further, we report the growth of self-assembled non-polar high indium clusters of In0.55Ga0.45N over non-polar (1 1 -2 0) a-plane In0.17Ga0.83N epilayer grown on a-plane (1 1 -2 0) GaN / (1 -1 0 2) r-plane sapphire substrate. The structure hence grown when investigated for photo-detecting properties, showed sensitivity to both infrared and ultraviolet radiations due to the different composition of InGaN region. Chapter 8 concludes with the summary of present investigations and the scope for future work.

碩士
國立中山大學
物理學系研究所
105
In this research, we grow m-plane gallium nitride on m-plane sapphire substrate using plasma-assisted molecular beam epitaxy (PAMBE)system with different plasma power and growth temperature. Then, we grow m-GaN doped Mn on the m-plane gallium nitride. A challenging issue in the growth of diluted magnetic semiconductors (DMSs)is secondary phase, and we suppress secondary phase controlling cell shutter to doped with Mn. GaN films are observed with their formation of surface and thickness. The crystal orientation and rocking curve are detected using high resolution X-ray diffraction (HRXRD). There are no observable secondary phase in the result of HRXRD. Nonpolar gallium nitride is anisotropy and calculating stress of film using Raman spectrum. The results of Raman scattering spectrum support Mn atoms substitutes Ga sites of GaN hexagonal structure. The results of superconductor quantum interference device (SQUID)show the ferromagnetic behavior at room temperature. Keywords: molecular beam epitaxy, m-plane GaN, nonpolar, m-plane sapphire

InGaN-based light emitters are strongly affected by the inhomogeneous broadening induced by random alloy fluctuations. While these effects have been extensively investigated on c-plane (e.g. localization of carriers at low carrier density due to potential fluctuations, delocalization at higher carrier density), much fewer work report on the impact of inhomogeneous broadening on the emission properties of semipolar and nonpolar InGaN quantum wells (QWs). In addition to have a higher electron- and hole-wavefunction overlap and thereby an increased radiative recombination rate thanks to the reduced/suppressed built-in electric field due to polarization discontinuities at heterointerfaces, QWs grown along semipolar/nonpolar crystal orientations have the interesting property to emit polarized light. The characterization and theoretical understanding of their optical polarization properties is the first main focus of this thesis. A correlation between spectral width and degree of linear polarization (DLP) is highlighted through extensive temperature- and excitation-dependent polarization-resolved confocal micro-photoluminescence spectroscopy carried out on planar semi-polar/nonpolar QWs and on the m-plane side facet of core-shell microrods. A theoretical model based on electronic band structure calculated by the kp-envelope function method is developed to explain this correlation by taking inhomogeneous broadening into account. Considering indium content fluctuations and the localization lengths of electrons and holes, different effective broadenings are applied to groups of subbands. It is shown that for high-inclination semipolar and nonpolar InGaN/GaN QWs inhomogeneous broadening leads to a significant increase of the DLP at room temperature. Furthermore, the DLP-drop towards high carrier density due to the transition from the Boltzmann- to the Fermi-regime is smoother and starts at lower carrier density. The model is also used to study the peculiar polarization properties of (202¯1) InGaN/GaN QWs compared to (202¯1¯) QWs: although they have equivalent band structures in the framework of k·p-theory and are therefore expected to have identical optical polarization properties, (202¯1) QWs consistently exhibit a lower DLP than (202¯1¯) QWs. This discrepancy might be related to different effective broadenings of their valence subbands induced by the rougher upper QW interface in (202¯1), by the larger sensitivity of holes to this upper interface due to the polarization field in (202¯1), and/or by the different degrees of localization of holes. Besides being strongly affected by inhomogeneous broadening, InGaN-based LEDs suffer from efficiency droop: their efficiency maximum is already reached at relatively low current density and then significantly drops towards their typical operation conditions. One way to mitigate its effect is to reduce the carrier density inside the active region, which can be achieved via several approaches, e.g. growing the active region on a 3D template, on a semipolar/nonpolar substrate or a relaxed InGaN template. The last two approaches reduce/suppress the built-in polarization field leading to wavefunctions with larger overlap and spread across the active region. In order to check and validate these approaches, a way to measure the carrier density inside the active region is necessary. This complex task, which is the second focus of this work, requires fitting a model of the carrier recombination dynamics to experimental data. Several methods are already available, which are mostly based on the basic ABC-model. The validity of this model is discussed through measurement of efficiency curves on various samples and extended to take into account the background carrier density at low carrier density and band-filling at high carrier density. The DLP drop towards high carrier density is fitted simultaneously with the efficiency curve to improve the robustness of the extraction of recombination coefficients. Nevertheless, without insights from time-resolved experimental data, extracting all recombination coefficients is shown to be very critical leading to ambiguous fitting results. Time-resolved measurements being complex and time-consuming, a new method based on an extended ABC-model and room-temperature bias-dependent photoluminescence spectroscopy is proposed. When investigating semipolar/nonpolar LEDs, this method allows to extract the carrier density within the active region without having to carry out time-resolved measurements, which is demonstrated using polarization-resolved efficiency curves measured on a m-plane LED. Growing the active region on 3D templates to reduce the local carrier density requires eventually experimental techniques with high spatial resolution for its characterization. This work reports the experimental know-how acquired through extensive characterization of single InGaN/GaN core-shell microrods. A thorough description of the confocal microscope and its alignment is given to achieve reproducible and diffraction limited spatial resolution polarization-resolved photoluminescence measurements, which allowed the first local internal quantum efficiency measurement along the side facet of InGaN/GaN core-shell microrods.
InGaN-basierte Lichtquellen sind stark von inhomogener Verbreiterung, die aus zufälligen Legierungsfluktuationen entsteht, beeinflusst. Während diese Effekte ausführlich auf die c-Ebene untersucht wurden (z.B. Ladungsträgerlokalisierung bei niedriger Ladungsträgerdichte auf Grund von Potentialfluktuationen, Delokalisierung bei höherer Ladungsträgerdichte), untersuchen wenige Studien den Einfluss von inhomogener Verbreiterung auf die Emissionseigenschaften von semipolarer und nonpolarer InGaN Quantentrögen. Quantentröge, die entlang semipolaren/nonpolaren Kristallrichtungen gewachsen sind, haben einen höheren Überlapp der Elektron- und Löcherwellenfunktionen und dadurch eine höhere strahlende Rekombinationsrate dank des niedrigen / unterdrückten elektrischen Feldes, das durch Polarizationsdiskontinuitäten an Heteroübergängen entsteht. Diese Quantentröge haben die interessante Eigenschaft, polariziertes Licht auszustrahlen. Die Charakterizierung und das theoretische Verständnis von diesen Polarizationseigenschaften ist der erste Schwerpunkt dieser Dissertation. Umfangreiche temperatur- und anregungsabhängige polarizationsaufgelöste konfokale Mikro-Photolumineszenz Spektroskopie auf planaren semipolaren/nonpolaren Quantentröge und auf die m-Ebene Seitenfacette von Core-Shell Mikrosäulen deuten auf eine Korrelation zwischen der spektralen Breite und dem optischen Polarizationsgrad. Basirend auf elektronischen Bandstrukturen, die mittels der k·p Hüllfunktionsmethode berechnet werden, wird ein theoretisches Modell entwickelt, um diese Korrelation unter Berücksichtigung der inhomogenen Verbreiterung zu erklären. In Anbetracht der Fluktuationen des Indiumgehalts und der Lokalisierungslängen von Elektronen und Löchern, werden unterschiedliche effektive Verbreiterungen auf Gruppen von Subbändern angewendet. Dadurch wird gezeigt, dass bei Raumtemperatur inhomogene Verbreiterung zu einem signifikanten Anstieg des Polarizationsgrads von semipolaren und nonpolaren InGaN/GaN Quantentrögen mit hoher Neigung führt. Darüber hinaus ist der Polarizationsgrad-Abfall bei höheren Ladungsträgerdichten aufgrund des Übergangs vom Boltzmann- zum Fermi-Regime glatter und beginnt bei niedrigerer Ladungsträgerdichte. Das Modell wird auch verwendet, um die besonderen Polarizationseigenschaften von (202¯1) InGaN/GaN Quantentrögen im Vergleich zu (202¯1¯) Quantentrögen zu untersuchen. Durch ihre äquivalenten Bandstrukturen im Rahmen der k·p-Theorie wird erwartet, dass sie ähnliche Polarizationseigenschaften zeigen. (202¯1) Quantentröge haben jedoch durchweg einen niedrigeren Polarizationsgrad als (202¯1¯) Quantentröge. Diese Diskrepanz könnte auf unterschiedliche effektive Verbreiterung ihrer Valenz-Subbänder zurückgeführt werden, die durch die rauere obere Quantentrog-Grenzfläche in (202¯1), durch die größere Empfindlichkeit der Löcher gegenüber dieser oberen Grenzfläche aufgrund des Polarizationsfelds in (202¯1) und /oder durch die unterschiedlichen Lokalisierungsgrade der Löcher induziert werden. InGaN LEDs sind nicht nur stark von inhomogener Verbreiterung beeinflusst, sondern leiden auch unter efficiency droop: Ihr Wirkungsgradmaximum wird bereits bei relativ geringer Stromdichte erreicht und fällt dann deutlich gegenüber ihrer typischen Betriebsbedingungen ab. Eine Möglichkeit, diesen Effekt abzuschwächen, ist, die Ladungsträgerdichte innerhalb des aktiven Bereichs zu verringern, was über verschiedene Ansätze erreicht werden kann. Die aktive Region kann zum Beispiel auf einer 3D-Pufferschicht, auf einem semipolaren/nonpolaren Substrat oder auf einer relaxierten InGaN-Pufferschicht gewachsen werden. Die letzten zwei Ansätze reduzieren/unterdrücken das Polarizationsfeld und führen dadurch zu Wellenfunktionen, die eine grössere Überlappung und Ausbreitung über die aktive Region haben. Damit diese Ansätze überprüft und validiert werden können, ist ein Verfahren erforderlich, um die Ladungsträgerdichte innerhalb der aktiven Region zu bestimmen. Diese komplexe Aufgabe, die den zweiten Schwerpunkt dieser Arbeit bildet, erfordert die Anpassung eines Modells der Ladungsträgerrekombinationsdynamik an experimentellen Daten. Die meisten Methoden, die bereits zur Verfügung stehen, nutzen das einfache ABC-Modell. Die Gültigkeit dieses Modells wird durch Messung von Effizienzkurven auf verschiedenen Proben diskutiert und erweitert, um die Hintergrungladungsträgerdichte bei niedriger Ladungsträgerdichte und Bandfüllung bei hoher Ladungsträgerdichte zu berücksichtigen. Der Polarizationsgrad-Abfall gegen hohe Ladungsträgerdichten wird gleichzeitig mit der Effizienzkurve angepasst, um das Bestimmen der Rekombinationskoeffizienten zu verbessern. Es ist jedoch sehr kritisch, alle Rekombinationskoeffizienten eindeutig zu bestimmen, ohne zeitaufgelöste experimentelle Daten zu berücksichtigen. Da zeitaufgelöste Messungen komplex und zeitaufwändig sind, wird eine neue Methode vorgeschlagen, die auf Bias-abhängiger Photolumineszenzspektroskopie bei Raumtemperatur und auf einem erweiterten ABC-Modell basiert. Bei der Untersuchung semipolarer/nonpolarer LEDs ermöglicht diese Methode das Bestimmen der Ladungsträgerdichte innerhalb der aktiven Region, ohne zeitaufgelöste Messungen durchführen zu müssen. Dies wird anhand polarizationsaufgelöster Effizienzkurven auf einer m-Ebene LED demonstriert. Das Wachsen der aktiven Region auf 3D-Pufferschichten zur Verringerung der lokalen Ladungsträgerdichte erfordert für ihre Charakterisierung experimentelle Techniken mit hoher räumlicher Auflösung. Diese Arbeit berichtet über das experimentelle Know-how, das durch die Charakterisierung einzelner InGaN/GaN Core-Shell Mikrosäulen erworben wurde. Eine gründliche Beschreibung des konfokalen Mikroskops und seiner Ausrichtung ist gegeben, um reproduzierbare polarizationsaufgelöste Photolumineszenzmessungen mit beugungsbegrenzter räumlicher Auflösung zu erreichen, die die ersten lokalen internen Quanteneffizienzmessungen entlang der Seitenfacette von InGaN/GaN Core-Shell Mikrosäulen ermöglichte.
Les sources lumineuses à base de InGaN sont fortement affectées par l'élargissement inhomogène dû aux fluctuations du taux d'indium. Alors que ces effets ont été étudiés extensivement sur le plan-c (par exemple: localisation des porteurs de charge à basse densité de porteurs dûe aux fluctuations de potentiel, délocalisation à plus haute densité de porteurs), seulement peu de travaux sont consacrés à l'étude de l'impact de l'élargissement inhomogène sur les propriétés d'émission des puits quantiques InGaN semipolaires et nonpolaires. En plus d'avoir un recouvrement plus grand des fonctions d'ondes des électrons et des trous, et par conséquent un taux de recombination radiatif plus élevé grâce à la réduction/suppression du champs électrique interne dû aux discontinuités de polarisation aux hétérointerfaces, les puits quantiques crûs dans les directions semipolaires/nonpolaires ont la propriété intéressante d'émettre de la lumière polarisée. La charactérisation et compréhension théorique de leurs propriétés de polarisation optique est l'un des axes de cette thèse. Une corrélation entre la largeur spectrale et le degré de polarisation linéaire (DLP = angl. degree of linear polarization) est mise en évidence par le biais de spectroscopie de micro-photoluminescence confocale résolue en polarisation en fonction de la température et de l'excitation éffectuée sur des puits quantiques planaires semipolaires et nonpolaires ainsi que sur les facettes latérales plan-m de micro-piliers core-shell. Un model théorique basé sur la structure de bandes électroniques calculée par la méthode k·p des fonctions d'enveloppe est développé pour expliquer cette corrélation en prenant l'élargissement inhomogène en compte. En considérant les fluctuations du taux d'indium et la longueur de localisation des électrons et des trous, des élargissements effectifs différents sont appliqués à des groupes de sous-bandes. Le modèle montre que pour les puits quantiques semipolaires/nonpolaires d'haute inclinaison l'élargissement inhomogène engendre une augmentation significative du DLP à température ambiante. De plus, vers les densités de porteurs plus élevées, la chute du DLP induite par la tansition du régime de Boltzmann au régime de Fermi est plus lente et commence à plus basse densité de porteurs. Le modèle est également utilisé pour étudié les propriétés particulières de polarisation optique des puits quantiques (202¯1) comparés aux puits (202¯1¯). Malgré qu'ils aient des structures de bandes équivalentes dans le cadre de la théorie k·p et devraient ainsi avoir des propriétés de polarisation optique identiques, les puits quantiques (202¯1) ont systématiquement un DLP plus bas que les puits quantiques (202¯1¯). Cette divergence est probablement liée aux élargissements effectifs différents qui s'appliquent à leurs sous-bandes de valence en raison de l'interface supérieure plus rugueuse du puit (202¯1), de la sensibilité des trous à l'interface supérieure du puit (202¯1) à cause du champ électrique interne, et/ou du différent degré de localisation des trous En plus d'être fortement affecté par l'élargissement inhomogène, les LEDs InGaN souffrent d'efficiency droop: leur efficacité maximale est atteinte déjà à une densité de courant relativement basse et baisse ensuite significativement vers leurs conditions d'opération typiques. Un moyen pour mitiger cet effet est de réduire la densité de courant dans la zone active, ce qui peut être atteint via plusieurs approches, notamment en croissant la région active sur un template 3D, sur un substrat semipolaire/nonpolaire ou un template d'InGaN relaxé. Les deux dernière approches diminuent/suppriment le champs électrique interne augmantant ainsi le recouvrement des fonctions d'onde et leur étendue dans la zone active. Afin de vérifier ces approches, une méthode pour déterminer la densité de porteurs dans la zone active est nécessaire. Cette tâche complexe, qui est le second axe de ce travail, requière d'ajuster un modèle de la dynamique de recombinaison des porteurs à des données expérimentales. La plupart des méthodes déjà disponibles se basent sur le simple modèle ABC. La validité de ce modèle est discutée à travers des courbes d'efficacité mesurées sur différents échantillons et étendue pour prendre en compte la densité de porteurs dûe au dopage à basse densité de porteurs ainsi que le remplissage des bandes à haute densité de porteurs. La chute du DLP vers les hautes densités de porteurs est ajustée simultanément à la courbe d'éfficacité pour augmenter la robustesse de la détermination des coefficients de recombinaison. Il est cependant montré que sans prendre en compte des données expériemntales résolues en temps il est très difficile d'extraire tous les coefficients de recombinaison sans ambiguosités. Les mesures résolues en temps étant complexes et longues, une nouvelle méthode basée sur un modèle ABC étendu et de la spectroscopie photoluminescence en fonction du bias à température ambiante est proposée. Lorsqu'elle est appliquée à des LEDs semipolaires/nonpolaires, elle permet d'extraire la densité de porteurs dans la région active sans devoir effectuer des mesures résolues en temps. La méthode est démontrée en utilisant des courbes d'efficacité résolues en polarisation measurées sur une LED plan-m. Croître la région active sur un template 3D afin de diminuer la densité locale de porteurs nécessite au final pour sa characterisation une technique expérimentale ayant une haute résolution spatiale. Ce travail résume le savoir-faire expérimental acquis en characterisant des micro-piliers core-shell InGaN/GaN uniques. Une description détaillée du microscope confocal et de son alignement est donnée pour atteindre des mesures de photoluminescence reproductibles et ayant une résolution limitée par la diffraction, ce qui a permis la première mesure locale d'efficacité interne quantique le long de la facette latérale de micro-piliers core-shell InGaN/GaN.