Le nitrure de gallium (GaN) et ses alliages ternaires et quaternaires suscitent de plus en plus d’intérêt dans les communautés scientifiques et industrielles pour leur potentiel d’utilisation dans des dispositifs électroniques haute fréquence, dans les transistors à forte mobilité électroniques, dans la photo-détection UV et les cellules solaires de nouvelles générations. L’aboutissement de ces nouveaux composants reste entravé à l’heure actuelle, entre autre, par la non maîtrise des techniques d’établissement de contacts électriques. C’est dans ce cadre général que s’inscrivent les travaux de cette thèse. Même si l’objectif principal de cette thèse concerne l’étude des défauts électriquement actifs dans les alliages de semiconducteurs à grand gap B(AlGa)N et de leur rôle dans les propriétés de transport, la réalisation des contacts ohmiques et des contacts Schottky constitue une étape essentielle dans la réalisation des dispositifs à étudier. Pour les contacts ohmiques, nous avons déposé des couches de type Ti/Al/Ti/Au (15/200/15/200) par évaporation thermique. Des résistances spécifiques des contacts de l’ordre de 3x10-4Wcm2 ont été déterminées par les méthodes des TLM linéaires et confirmées par les TLM circulaires. Une modélisation théorique a été entreprise dans ce sens pour analyser les mesures expérimentales. Ensuite on a réalisé des diodes Schottky en déposant des contacts métalliques de Platine (Pt) d’épaisseur 150 nm. Des facteurs d’idéalité de 1.3 et une hauteur de barrière de 0.76 eV ont été obtenus et d’une manière reproductible. Une fois ces dispositifs réalisés, une étude des mécanismes de transport a été entreprise et nous a permis de mettre en évidence l’existence des effets tunnel direct et assisté par le champ, en plus de l’effet thermoïonique classique. Ceci a été mis en évidence par des mesures de courant et de capacité en fonction de la température. Pour les photodétecteurs, nous avons réalisés les mêmes mesures de courant et de capacité à l’obscurité et sous illumination à des longueurs d’ondes adaptées. Ces mesures nous ont permis de comprendre les phénomènes de gain qu’on a observés sur ces échantillons et aussi de mettre en évidence des mécanismes thermiquement actifs, dont les énergies d’activation ont été déterminées par la technique de l’Arrhenius. L’étude des défauts électriquement actifs a été menée par la technique transitoire de capacité de niveaux profonds, la (DLTS). Cette technique a été récemment mise en oeuvre au laboratoire et nous a permis d’effectuer des mesures sous différentes conditions incluant diverses polarisations de repos, différentes fréquences, et différentes hauteurs et largeurs d’impulsion de polarisation. Un des résultats importants est la possibilité de caractérisation à la fois des pièges à majoritaires et des pièges à minoritaire en changeant simplement les conditions de polarisation et contrairement aux procédures habituelles où une excitation optique supplémentaire est souvent nécessaire pour augmenter la concentration des porteurs minoritaires. Il a ainsi été mis en évidence, en accord avec la plupart des résultats de la littérature, l’existence de 6 pièges à électrons, tous situés en dessous de 0.9 eV de la bande de conduction, de trois pièges à trous dans l’intervalle 0.6 - 0 .7 eV au dessus de la bande de valence et un piège à trous distribué à l’interface. Une procédure rigoureuse de fit a été mise au point et a permis de confirmer nos résultats obtenus par la procédure classique de l’Arrhenius / Gallium nitride (GaN) and its ternary and quaternary alloys are attracting more and more interest in the scientific and industrial communities for their potential for use in high frequency electronic devices, for transistors with high electronic mobility, for UV photo-detection and new-generation solar cells. The outcome of these new components is still be seen to be limited in many areas, mainly due to the lack of control of electrical contacts implementation techniques. It is in this context that this thesis takes place.Although the main objective of this thesis deals with the study of the electrically active defects in high band gap B(AlGa)N semiconductor alloys and their role in the transport properties, the production of ohmic and Schottky contacts is an essential step in the realization of the devices under study. For the Ohmic contacts, we have deposited Ti/Al/Ti/Au (15/200/15/200) layers by thermal evaporation. Using the Transfer Length Method (TLM), we obtained specific contact resistances in the order of 3x10-4Wcm2. The Circular TLM has also confirmed this result. Besides, a theoretical modelling has been carried out to analyse the experimental measurements. Schottky diodes were then produced by depositing 150 nm platinum (Pt) metal contacts. An ideality factor of 1.3 and a barrier height of 0.76 eV were obtained. On the other hand, a study of transport mechanisms has been performed. It allowed us to demonstrate the existence of the direct tunnelling and the Thermionic Field Emission, in addition to the conventional thermionic effect. This result was underpinned by current and capacity measurements as a function of temperature. For photo detectors, we performed the same measurements of current and capacity in darkness and under illumination at suitable wavelengths. These measurements allowed understanding the internal gain that was observed on the samples. Furthermore, they show the effect of the thermally active mechanisms whose activation energies were determined by the Arrhenius technique. Using the Deep-Level Transient Spectroscopy (DLTS) technique followed up the study of the electrically active defects. This technique has recently been implemented in the laboratory. It allowed us to perform measurements under different conditions including various reverse bias, different frequencies, and different voltage pulse amplitudes and durations. One of the important results is the possibility of characterizing both majority and minority traps by simply changing the polarization conditions, as opposed to the usual procedures where an additional optical excitation is often necessary to increase the concentration of the minority carriers. In accordance with most of the encountered literature results, we found 6 electron traps all located below 0.9 eV of the conduction band, 3 hole traps in the 0.6-0.7 eV range above the valence band and one hole trap distributed at the interface. A rigorous procedure was developed and confirmed our results obtained by the standard Arrhenius technique

The understanding of the electrical properties of defects introducing deep levels in silicon is of prime technological importance in modern microelectronics. In this thesis, a comprehensive study of the transition metals titanium, cobalt, and nickel in silicon, and of their interaction with hydrogen is presented. The formed defects are detected and characterized by deep level transient spectroscopy (DLTS), Laplace DLTS, and minority carrier transient spectroscopy. A natural starting point for a study of metal-hydrogen reactions in silicon is the analysis of the effect of hydrogen on metal-free silicon. Complexes of hydrogen with carbon, which create deep levels in the band gap of silicon, are observed. Titanium introduces three levels into the band gap. The charge states determined in this thesis are in contradiction to the literature, questioning the assignment of these levels. Upon hydrogenation, TiH complexes with one, two, and three hydrogen atoms are identified. A proposition by theory that two different configurations of TiH with one hydrogen atom exist, can be supported. Cobalt is shown to have only one level in the band gap of silicon, whereas a second level previously attributed to cobalt is assigned to the cobalt-boron pair. Two CoH complexes are determined. Nickel has three levels in the band gap. Upon hydrogenation, complexes with up to three hydrogen atoms are identified. One of the defects can be observed in both n - and p -type silicon. For all three metals investigated, passive hydrogen complexes exist. They are created by further hydrogenation after the appearance of the above mentioned electrically active complexes. The thesis concludes with a comparison of the obtained results with those of neighboring elements to look for similarities and patterns. / Das Verständnis der elektrischen Eigenschaften von Defekten, welche tiefe Niveaus in der Bandlücke von Silizium erzeugen, ist von außerordentlichem Interesse für die moderne Mikroelektronik. In der vorliegenden Dissertation wird eine umfassende Untersuchung der Übergangsmetalle Titan, Kobalt und Nickel in Silizium und ihrer Wechselwirkung mit Wasserstoff vorgestellt. Die entstandenen Defekte werden mit Hilfe von Kapazitätstransientenspektroskopie (DLTS - deep level transient spectroscopy), Laplace DLTS und Minoritätsladungsträgertransientenspektroskopie (MCTS - minority carrier transient spectroscopy) beobachtet und charakterisiert. Für eine fehlerfreie Analyse der Metall-Wasserstoff-Reaktionen ist es sinnvoll, zuerst den Einfluss des Wasserstoffs auf metallfreies Silizium zu prüfen. Dabei wird die Bildung von Kohlenstoff-Wasserstoff-Komplexen, welche Niveaus in der Bandlücke von Silizium erzeugen, beobachtet. Titan besitzt drei Niveaus in der Bandlücke von Silizium. Die in dieser Arbeit bestimmten Ladungszustände stehen im Widerspruch zu den Literaturangaben, daher wird die Zuordnung dieser Niveaus in Frage gestellt. Die Reaktion von Titan mit Wasserstoff führt zu elektrisch aktiven Komplexen mit bis zu drei Wasserstoffatomen. Die Ergebnisse unterstützen einen Vorschlag aus der Theorie, nach dem der Komplex mit einem Wasserstoff zwei verschiedene Konfigurationen besitzen soll. Kobalt erzeugt ein Niveau in der Bandlücke. Ein weiteres Niveau, welches früher ebenfalls dem Kobalt zugewiesen wurde, kann dem Kobalt-Bor-Paar zugeordnet werden. Nach der Reaktion mit Wasserstoff können zwei CoH-Komplexe nachgewiesen werden. Nickel besitzt drei Niveaus in der Bandlücke und erzeugt elektrisch aktive NiH-Komplexe mit bis zu drei Wasserstoffatomen. Einer dieser Defekte kann sowohl im n - als auch im p -Typ Silizium beobachtet werden. Alle drei untersuchten Metalle besitzen elektrisch passive Komplexe, welche nach der weiteren Reaktion von Wasserstoff mit den aktiven Komplexen entstehen. Die Arbeit endet mit einem Vergleich der Ergebnisse mit denen benachbarter Elemente, um mögliche Ähnlichkeiten oder Muster zu erkennen.

No description available.

Non-volatile memory can keep the data without supplying power, and it is suitable for portable electronic products due to the advantage of low power consumption. In current industrial production, high-temperature and long-time process are necessary for the fabrication of non-volatile memory, which are heavy loadings on production capacity and lots cost. Therefore, decreasing the temperature of the process is a trend. Recently using the oxidation treatment of supercritical carbon dioxide fluid can efficiently decrease the temperature of the process. In this thesis, the mixture layer of Zn, Sn, and SiO2 is applied to reduce the temperature of process, and to employ the defects of ZnO and SnO2 as floating gate for electron storage to fabricate the nonvolatile memory device. Zn and Sn are applied due to the low temperature melting points. To ensure the layer of cosputtering with Zn and Sn to be able to successfully fabricate as nano material device, the process of traditional rapid temperature annealing treatment was applied for first step. The co-sputtered Zn-Sn-SiO2 thin film was deposited on the tunneling oxide layer, and then the thin film was treated with varied annealing temperature to precipitate ZnO and SnO2 nanocrystals. After that, the C-V measurement is applied to analyze the change of the electrical and material properties. Using a positive bias, the electrons are injected into the oxide layer, by the threshold voltage the offset is occurred, which is defined as the memory window of the memory effect, and the property of nonvolatile memory will be applied. In addition, no matter the charge is injected from the gate oxide or tunnel oxide, the defects position of DLTS¡¦s peak is with the same property. The supercritical carbon dioxide fluid technology has been performed to study the memory effect. The capability of electron injection, storages and the defect, in the storage layer were studied by the C-V measurement and DLTS. The experiment confirmed that the Zn-Sn alloy has the memory property after it been treated by the supercritical carbon dioxide fluid technology. It has shown that Zn can promote to the storage capability ability due to the formation of deep level defects of SnO2 from the DLTS spectra. A new species is found at 0.93 eV with low activation energy and high capability of electron storage. The defect formation mechanism of Zn, ZnO, Zn-O-Si, Sn, and SnO are analyzed by found by the XPS and DLTS. The device fabrication using Zn-Si alloy and supercritical carbon dioxide fluid technology has the potential to reduce the process temperature and to improve the memory property of nonvolatile memory device.

Das PICTS-Verfahren ist eine der am häufigsten eingesetzten Methoden zur Charakterisierung semiisolierender Halbleiter. Die methodischen Fortschritte bei der Ermittlung von Störstellenparametern mit diesem Verfahren werden in dieser Arbeit vorgestellt. Als praktikable Methode für den Nachweis einer temperaturabhängigen Änderung des Besetzungsverhältnisses einer Haftstelle wird die Normierung auf die Emissionsrate der Elektronen eingeführt. Es wird gezeigt, dass Peaks, bei denen diese Normierung misslingt, nicht für die Ermittlung der Störstellenparameter herangezogen werden dürfen. Die Untersuchungen belegen, dass für die vollständige Umladung der Störstellen eine geeignete Anregungsintensität verwendet werden muss. Durch PICTS-Messungen an Kupfer-dotierten Proben wird eine systematische Abhängigkeit der Peakhöhen Kupfer-korrelierter Peaks vom Kupfergehalt der Proben nachgewiesen. Mit den Untersuchungen wird belegt, dass sich Kupfer mittels PICTS bis zu einer minimalen AES-Kupfer-Konzentration von [Cu]min ca. 5·1E14/cm^3 nachweisen lässt.

Das Halbleitermaterial Zinkselenid (ZnSe) wurde mit Deep Level Transient Spectroscopy (DLTS) untersucht. Fuer planar N-dotierte, MO-CVD-gewachsene ZnSe-Schichten auf p-GaAs wurden vorwiegend breite Zustandsverteilungen, aber auch tiefe Niveaus gefunden. In kristallin gezuechtetem, undotiertem ZnSe wurden tiefe Stoerstellen nachgewiesen.

ZnO material based hetero-junctions are a potential candidate for the design andrealization of intrinsic white light emitting devices (WLEDs) due to several advantages overthe nitride based material system. During the last few years the lack of a reliable andreproducible p-type doping in ZnO material with sufficiently high conductivity and carrierconcentration has initiated an alternative approach to grow n-ZnO nanorods (NRs) on other ptypeinorganic and organic substrates. This thesis deals with ZnO NRs-hetero-junctions basedintrinsic WLEDs grown on p-SiC, n-SiC and p-type polymers. The NRs were grown by thelow temperature aqueous chemical growth (ACG) and the high temperature vapor liquid solid(VLS) method. The structural, electrical and optical properties of these WLEDs wereinvestigated and analyzed by means of scanning electron microscope (SEM), current voltage(I-V), photoluminescence (PL), cathodoluminescence (CL), electroluminescence (EL) anddeep level transient spectroscopy (DLTS). Room temperature (RT) PL spectra of ZnOtypically exhibit one sharp UV peak and possibly one or two broad deep level emissions(DLE) due to deep level defects in the bandgap. For obtaining detailed information about thephysical origin, growth dependence of optically active defects and their spatial distribution,especially to study the re-absorption of the UV in hetero-junction WLEDs structure depthresolved CL spectroscopy, is performed. At room temperature the CL intensity of the DLEband is increased with the increase of the electron beam penetration depth due to the increaseof the defect concentration at the ZnO NRs/substrate interface. The intensity ratio of the DLEto the UV emission, which is very useful in exploring the origin of the deep level emissionand the distribution of the recombination centers, is monitored. It was found that the deepcenters are distributed exponentially along the ZnO NRs and that there are more deep defectsat the root of ZnO NRs compared to the upper part. The RT-EL spectra of WLEDs illustrateemission band covering the whole visible range from 420 nm and up to 800 nm. The whitelightcomponents are distinguished using a Gaussian function and the components were foundto be violet, blue, green, orange and red emission lines. The origin of these emission lines wasfurther identified. Color coordinates measurement of the WLEDs reveals that the emitted lighthas a white impression. The color rendering index (CRI) and the correlated color temperature(CCT) of the fabricated WLEDs were calculated to be 80-92 and 3300-4200 K, respectively.

This thesis concerns new hydrogen- and polarity-related effects in the photoluminescence of ZnO single crystal wafers and the relationship between surface electron accumulation and surface hydroxyl coverage on different ZnO surfaces. A comparative study of the low temperature photoluminescence of various types of hydrothermal and melt-grown ZnO wafers revealed several new hydrogen-related exciton recombination lines and a number of consistent polarity-related differences in the PL emission from different crystallographic surfaces. Temperature-dependent PL measurements were extensively used to distinguish the ground and excited state transitions involved in these effects. ZnO samples of different surface polarity were annealed in oxygen and nitrogen gases and in hydrogen-containing forming gas mixtures in an attempt to identify the origin of these new PL features. The well known aluminium-related I_₆ recombination line was resolved into two separate features in hydrothermal ZnO, and the new component I6-H (3.36081 eV) was found to repeatedly quench and then re-emerge after annealing in oxygen and forming gas, respectively. A model involving an aluminium - lithium - hydrogen defect complex was proposed for I6-H and further tested via hydrogen and deuterium implantation experiments on hydrothermal ZnO wafers with different lithium concentrations. These experiments also provided evidence for the involvement of a different lithium-hydrogen defect complex in other hydrogen-related emission lines I₄b,c (3.36219 eV and 3.36237 eV) unique to hydrothermal ZnO. In addition, a broad Gaussian-shaped feature observed in the near-band-edge PL emission from the O-polar (000‾1), a-plane (11‾20) and r-plane (1‾102) faces of ZnO was shown to be surface sensitive and also related to hydrogen. The involvement of hydrogen in the chemical and electronic properties of different ZnO surfaces was also investigated. The thermal stability of the hydroxyl termination and the associated downward surface band bending on the polar and non-polar surfaces of ZnO was studied by synchrotron and real-time photoelectron spectroscopy, both during and after annealing and subsequent H₂O/H₂ dosing in ultra-high vacuum conditions. On the O-polar face, the band bending could be reversibly switched over a range of approximately 0.8 eV by adjusting the surface H-coverage using simple UHV heat treatments and atmospheric exposure. A transition from electron accumulation to electron depletion on the O-polar face was observed at a H-coverage of approximately 0.9 monolayers. In contrast, the downward band bending on the Zn-polar face was significantly more resilient and electron-depleted surfaces could not be prepared by heat treatment alone. This was also the case for in situ cleaving in UHV conditions which failed to produce hydroxyl-free surfaces due to migration of hydrogen from the bulk to the cleaved surface. Interestingly, the thermal stability of the hydroxyl termination on the a-plane (11‾20) and m-plane (10‾10) surfaces was signiifcantly lower than on the polar faces due to the availability of a lower energy desorption pathway and the electrostatic stability of these non-polar surfaces in their clean, bulk terminated form. The surface band bending on the non-polar ZnO surfaces was also found to be directly related to their OH coverage with a transition from downward to upward band bending, similar to that observed on the O-polar face, as the OH coverage was reduced. Thermal admittance spectroscopy and deep level transient spectroscopy was used to investigate the effect of lithium removal on the defect nature of hydrothermal ZnO. A number of new defects were introduced by the high temperature (1100-1400°C) annealing/re-polishing process used to reduce the lithium concentration, particularly E₁₉₀ (also known as T2) which is thought to be related to Zn vacancies. Significantly, both the E₅₀ defect level and the I6-H PL emission line were absent after lithium (and hydrogen) removal suggesting an association of both these features with the same aluminium - lithium - hydrogen defect complex.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23901号 / 工博第4988号 / 新制||工||1779(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 田中 功, 教授 杉村 博之, 准教授 野瀬 嘉太郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第17579号 / 工博第3738号 / 新制||工||1570(附属図書館) / 30345 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 髙岡 義寛, 准教授 船戸 充 / 学位規則第4条第1項該当