Dissertations / Theses on the topic 'Bipolar switching'

Two MOS-Bipolar composite power semiconductor switching devices are proposed and experimentally demonstrated. These devices feature high voltage and high current capabilities, fast switching speeds, simple gate drive requirements, savings in chip area, reverse bias second breakdown ruggedness and large safe operating areas. Application characteristics of the devices for high frequency power inverter circuits are discussed. Monolithic integration of the two composite devices are also proposed.<br>Ph. D.

The use of Insulated Gate Bipolar Transistors (IGBT) have enabled better switching performance than the Metal Oxide Semiconductor Field effect Transistor (MOSFET) in medium to high power applications due to their lower on-state power loss and higher current densities. The power ratings of IGBTs are slowly increasing and are envisaged to replace thyristors in medium power applications such as High Voltage Direct Current (HVDC) inverter systems and traction drive controls. Devices such as the MOS Controlled Thyristor (MCT) and Emitter Switched Thyristor (EST) were developed in an effort to further simplify drive requirements of thyristors by incorporating a voltage controlled MOS gate into the thyristor structure. However, the MCT is unable to achieve controlled current saturation which is a desirable characteristic of power switching devices while the EST has only limited control. The IGBT can achieve current saturation, however, due to the transistor based structure it exhibits a larger on-state voltage in high power applications compared with thyristor based devices. MOS Gated Thyristor (MGT) devices are a promising alternative to transistor based devices as they exhibit a lower forward voltage drop and improved current densities. This current research focuses on the Clustered Insulated Gate Bipolar Transistor (CIGBT) whilst being operated under soft-switching regimes. The CIGBT is a MOS gated thyristor device that exhibits a unique self-clamping feature that protects cathode cells from high anode voltages under all operating conditions. The self-clamping feature also enables current saturation at high gate biases and provides low switching losses. Its low on-state voltage and high voltage blocking capabilities make the CIGBT suitable as a contender to the IGBT in medium to high power switching applications. For the first time, the CIGBT has been operated under soft-switching regimes and transient over-voltages at turn-on have been witnessed which have been found to be associated with a number of factors. The internal dynamics of the CIGBT have been analysed using 2D numerical simulations and it has been shown that a major influence on the peak voltage is the P well spacing within the CIGBT structure. For example, Small adjacent P well spacings within the device results in an inability for the CIGBT to switch iv on correctly. Further to this, implant concentrations of the n well region during device fabrication can also affect the turn-on transients. Despite this, the CIGBT has been experimental analysed under soft-switching conditions and found to outperform the IGBT by 12% and 27% for on-state voltage drop and total energy losses respectively. Turn off current bumps have been seen whilst switching the device in zero voltage and zero current switching mode of operation and the internal dynamics have been analysed to show the influence upon the current at turn off. Preliminary results on the Trench CIGBT (TCIGBT) under soft switching conditions has also been analysed for the first time and was found to have a reduced peak over-voltage and better switching performance than the planer CIGBT. Through optimisation of the CIGBT structure and fabrication process, it is seen that the device will become a suitable replacement to IGBT in medium power application.

Commutation is a fundamental feature of all DC machines. In conventional DC machines the commutation function is performed by the commutator and brushes. These act as both position sensors and switches. The mechanical commutator has obvious disadvantages. Overcoming those disadvantages has been a major reason behind the development of brushless DC (BLDC) machines. In brushless DC machines commutation is performed by power electronic devices forming part of an inverter bridge. However, switching of the power electronic devices has to be synchronised with rotor position. Position sensing is therefore an essential requirement. This can be done by using sensors such as Hall Effect devices or a sensorless approach may be adopted. Advantages of sensorless techniques include reduced cost and wiring. The most common sensorless method is based on detection of the zero crossing of back EMF signals. But this technique works only above a certain speed since back EMF is directly proportional to speed. As a result BLDC systems which rely solely on back EMF signals for commutation suffer from relatively poor starting performance characterised by back rotation of up to one hundred and eigthty electrical degrees and large fluctuations in electromagnetic torque resulting from non-ideal commutation instants. This may not be acceptable for some applications and many researchers have attempted to overcome those problems. The aim of this project has been to investigate the possibility of a sensorless technique which does not cost more than the back EMF method but with a performance at start-up comparable with that obtained when Hall sensors are used. Initial investigations led to a saliency based method. Detailed theoretical analysis is presented which shows that the method is insensitive to variations in operational parameters such as load current and circuit parameters such as power device voltage drops and winding resistances. There is a close parallel between it and the back EMF method and this makes it easy to swap to the latter method at high speed if necessary. A starting strategy, relying on saliency related measurements, is proposed which offers starting performance much better than the back EMF method and almost as good as Hall sensor based techniques. Experimental evidence is provided to confirm that commutation instants determined by the proposed method are practically coincident with those obtained when Hall sensors are used.

Over the last few years, the non-volatile memories (NVM) have been dominating the research of the storage elements. The resistance random-access memory (RRAM) and the memristor that employs the resistive switching (RS) mechanism appear to be potential candidates for NVM. Among the RS materials that were reported is the TaOx which showed surprising RS performance. This oxide material has been widely used to construct a metal-insulator-semiconductor-metal (MISM) RRAM which can be referred to as bi-layered RRAM. This bi-layered RRAM consists of TaOx as a bulk material and Ta2O5 as an insulator layer, sandwiched between two platinum electrodes to form Pt/Ta2O5/TaOx/Pt RRAM. However, a physics-based mathematical model of this RRAM is required to further study the detailed physics behind its conduction mechanism and the RS process. In addition to the mathematical model, a SPICE model is also required to understand the behaviour of this bi-layered RRAM device when integrated in memory design for the future generation storage devices or when used in RRAM-based circuit applications. This doctoral research presents novel mathematical and SPICE models of a bipolar resistive switching (BRS) of the Pt/Ta2O5/TaOx/Pt bi-layered RRAM. For this purpose, MATLAB and LTSPICE are used to design the mathematical and the SPICE bi-layered RRAM models, respectively, and the obtained simulation results for both models are compared with the experimental data from SAMSUNG labs. The novelty of the mathematical model lies in incorporating the tunnelling probability factor (TPF) between the semiconductor and the metal layers and therefore, demonstrating its effect on the conduction mechanism. In addition, the effect of continuous variation of the interface traps densities and the ideality factor during BRS is modelled using the semiconductor properties and the characteristics of the metal-insulator-semiconductor (MIS) system. Thus, the model emphasizes the dependency of the device current on the physical characteristics of the insulator layer. Moreover, the electric field equation for the active region is derived for the MISM structure which is used together with Mott and Gurney rigid point-ion model and Joule heating effect to model the oxygen ion migration mechanism. Finally, the model also demonstrates the self-limiting growth of the doped region. The proposed SPICE model emphasizes the impact of the change in the switching layer thickness on the device behaviour at low resistance state (LRS), high resistance state (HRS), and the transitional period. The validity of the SPICE model is verified through using three different sets of experimental data from Pt/Ta2O5/TaOx/Pt RRAM with switching layer thickness smaller than 5 nm. The SPICE model reproduced all the major features from the experimental results for the SET and RESET processes and also the asymmetric and the symmetric characteristics in HRS and LRS, respectively. The SPICE model matches the measured experimental results with an average error of < 11%. It also showed stable behaviour for its HRS and LRS regions under different types of input signals. The model is parameterized in order to fit into Ta2O5/TaOx RRAM devices with switching layer thickness smaller than 5 nm, thus, facilitating the model usage. The SPICE model can be included in the SPICE-compatible circuit simulation and is suitable for the exploration of the Ta2O5/TaOx bi-layered RRAM device performance at circuit level. At the end of the research, a metal-insulator-metal (MIM) RRAM SPICE model of Ta/TaOx/Pt is developed which can be used in the future work to compare between the MISM and MIM TaOx-based RRAM devices.

The downscaling of transistors is assumed to come to an end within the next years, and the semiconductor nonvolatile memories are facing the same physical downscaling challenge. Therefore, it is necessary to consider new computing paradigms and new memory concepts. Resistive switching devices (also referred to as memristive switches) are two-terminal passive device, which offer a nonvolatile switching behavior by applying short bias pulses. They have been considered as one of the most promising candidates for next generation memory and nonvolatile logic applications. They provide the possibility to carry out the information processing and storage simultaneously using the same resistive switching device. This dissertation focuses on the fabrication and characterization of BiFeO3 (BFO)-based metal-insulator-metal (MIM) devices in order to exploit the potential applications in nonvolatile memory and nonvolatile reconfigurable logics. Electroforming-free bipolar resistive switching was observed in MIM structures with BFO single layer thin film. The resistive switching mechanism is understood by a model of a tunable bottom Schottky barrier. The oxygen vacancies act as the mobile donors which can be redistributed under the writing bias to change the bottom Schottky barrier height and consequently change the resistance of the MIM structures. The Ti atoms diffusing from the bottom electrode act as the fixed donors which can effectively trap and release oxygen vacancies and consequently stabilize the resistive switching characteristics. The resistive switching behavior can be engineered by Ti implantation of the bottom electrodes. MIM structures with BiFeO3/Ti:BiFeO3 (BFO/BFTO) bilayer thin films show nonvolatile resistive switching behavior in both positive and negative bias range without electroforming process. The resistance state of BFO/BFTO bilayer structures depends not only on the writing bias, but also on the polarity of reading bias. For reconfigurable logic applications, the polarity of the reading bias can be used as an additional logic variable, which makes it feasible to program and store all 16 Boolean logic functions simultaneously into the same single cell of BFO/BFTO bilayer MIM structure in three logic cycles<br>Die Herunterskalierung von Transistoren für die Informationsverarbeitung in der Halbleiterindustrie wird in den nächsten Jahren zu einem Ende kommen. Auch die Herunterskalierung von nichtflüchtigen Speichern für die Informationsspeicherung sieht ähnlichen Herausforderungen entgegen. Es ist daher notwendig, neue IT-Paradigmen und neue Speicherkonzepte zu entwickeln. Das Widerstandsschaltbauelement ist ein elektrisches passives Bauelement, in dem ein der Widerstand mittels elektrischer Spannungspulse geändert wird. Solche Widerstandsschaltbauelemente zählen zu den aussichtsreichsten Kandidaten für die nächste Generation von nichtflüchtigen Speichern sowie für eine rekonfigurierbare Logik. Sie bieten die Möglichkeit zur gleichzeitigen Informationsverarbeitung und -speicherung. Der Fokus der vorliegenden Arbeit liegt bei der Herstellung und der Charakterisierung von BiFeO 3 (BFO)-basierenden Metal-insulator-Metall (MIM) Strukturen, um zukünftig deren Anwendung in nichtflüchtigen Speichern und in rekonfigurierbaren Logikschaltungen zu ermöglichen. Das Widerstandsschalten wurde in MIM-Strukturen mit einer BFO-Einzelschicht untersucht. Ein besonderes Merkmal von BFO-basierten MIM-Strukturen ist es, dass keine elektrische Formierung notwendig ist. Der Widerstandsschaltmechnismus wird durch das Modell einer variierten Schottky-Barriere erklärt. Dabei dienen Sauerstoff-Vakanzen im BFO als beweglichen Donatoren, die unter der Wirkung eines elektrischen Schreibspannungspulses nichtflüchtig umverteilt werden und die Schottky-Barriere des Bottom-Metallkontaktes ändern. Dabei spielen die während der Herstellung von BFO substitutionell eingebaute Ti-Donatoren in der Nähe des Bottom-Metallkontaktes eine wesentliche Rolle. Die Ti-Donatoren fangen Sauerstoff-Vakanzen beim Anlegen eines positiven elektrischen Schreibspannungspulses ein oder lassen diese beim Anlegen eines negativen elektrischen Schreibspannungspules wieder frei. Es wurde gezeigt, dass die Ti-Donatoren auch durch Ti-Implantation der Bottom-Elektrode in das System eingebracht werden können. MIM-Strukturen mit BiFeO 3 /Ti:BiFeO 3 (BFO/BFTO) Zweischichten weisen substitutionell eingebaute Ti-Donatoren sowohl nahe der Bottom-Elektrode als auch nahe der Top-Elektrode auf. Sie zeigen nichtflüchtiges, komplementäres Widerstandsschalten mit einer komplementär variierbaren Schottky-Barriere an der Bottom-Elektrode und an der Top-Elektrode ohne elektrische Formierung. Der Widerstand der BFO/BFTO-MIM-Strukturen hängt nicht nur von der Schreibspannung, sondern auch von der Polarität der Lesespannung ab. Für die rekonfigurierbaren logischen Anwendungen kann die Polarität der Lesespannung als zusätzliche Logikvariable verwendet werden. Damit gelingt die Programmierung und Speicherung aller 16 Booleschen Logik-Funktionen mit drei logischen Zyklen in dieselbe BFTO/BFO MIM-Struktur

L'agressivité de l'environnement radiatif spatial constitue une cause majeure de défaillance des composants et systèmes embarqués sur les satellites. Les transistors bipolaires sont sensibles au rayonnement ionisant et peuvent présenter un effet de débit de dose (ELDRS). Une plus forte dégradation est alors observée à faible débit de dose. Les normes actuelles de test ne permettent pas de prendre en compte entièrement cette sensibilité au débit. La nouvelle méthode de test dite des Débits commutés prend en compte cet effet d'ELDRS. Une charge utile développée sur le satellite Robusta et présentée ici va permettre une première validation de la méthode. Des amplificateurs classiques (VFA) dont la sensibilité en dose bien connue et induit des effets circuit, c'est-à-dire une dégradation non monotone des paramètres liés à des phénomènes antagonistes, seront embarqués sur le satellite robusta et serviront à la validation de la méthode. La charge utile du satellite est composée de LM124 et LM139. Le choix du faible débit et des différentes commutations appliquées s'est appuyé sur l'analyse radiation de la mission. Cette méthode a permis de tester les composants à faible débit de dose dans un temps moitié moindre qu'un test faible débit. Les résultats produits pourront par la suite, après mise en orbite de Robusta, être comparés à des données faible débit obtenues en vol.Une seconde étude sur des amplificateurs à convoyeur de courant (CFA), jusque là très peu étudiés, a démontré la sensibilité à la dose de ce type d'amplificateur et mis en évidence de nouveaux effets circuits. Cette étude a été réalisée au moyen de trois types d'irradiations différentes et s'appuie sur une analyse circuit. Les irradiations et l'étude circuit menées ont montré que l'amplitude des dégradations des différents paramètres étudiés est aléatoire et dépend de la symétrie plus ou moins parfaite du circuit : une différence de process entre deux transistors va induire une dégradation plus ou moins importante des paramètres. Ces premiers travaux serviront de base à différentes études, et notamment à l'étude des effets de synergie dose/SET ou de synergie dose/CEM sur les CFA<br>The aggressive space radiation environment constitutes a major cause of failure for components and systems on board the satellites. Bipolar transistors are know to be sensitive to ionizing radiation and may present dose rate effect (ELDRS). A greater degradation is observed at low dose rate. Current standards test methods can not fully take into account this sensitivity to the dose rate. The new Dose rate Switching test methodology takes into account this ELDRS effect. A Payload developed on the Robusta satellite and presented here will allow a first validation of the method. Classical amplifier (VFA) whose dose rate sensibility is well known and induce circuit effects, that means a non monotonous degradation of parameters related to antagonist phenomena, will be loaded on board Robusta satellite and used to validated the method. The satellite Payload is composed of LM124 and LM139. The low dose rate choice and the different switching applied relied on mission radiation analysis. This method allowed to reproduce the dose induced degradation of the components in half the time it takes at low dose rate. The results produced can then, after Robusta is launched, be compared to low dose rate data obtained in flight. A second study on current conveyor amplifier (CFA), so far very little studied, demonstrated the sensitivity to ionizing dose of this type of amplifier and identified new effects circuits. This study was conducted using three different types of irradiation and based on a circuit analysis. Irradiations and circuit analysis have shown that the amplitude of the degradation measured on the different parameters studied is erratic and depends on the perfect symmetry of the circuit: a slight discrepancy in the process between two transistors will induce a more or less significant symmetry in the parameters degradation. This early work will be a base for various studies, including the study of synergy dose/SET or synergy dose/EMC on CFA

This project is made for a deeper understanding ofhow frequency and amplitude of the waves that create the controlwave in a Pulse Width Modulated 2-level inverter affect the powerquality and power losses. The results were that a high frequencyreduces the Total Harmonic Distortion but increases the powerloss. The amplitude, however, reduces both the Total HarmonicDistortion and the power loss as it increases. All the analyseswere done in a simulation program called Simulink. The resultscan be applied when improving High Voltage Direct Currentinverters to develop a functional High Voltage Direct Currentgrid that enables wider use of renewable energy sources.<br>Projektet syftar till att få en djupare förståelse för hur frekvensen och amplituden på de vågor som skapar kontollvågen i en pulsbreddsmodulerad likspänningsomvandlare med två nivåer påverkar effektkvalitén och effektförlusterna. Resultatet av studien var att en hög frekvens minskar ”Total Harmonic Distortion” men ökar effektförlusterna. Amplituden å andra sidan reducerar både ”Total Harmonic Distortion” och effektförlusterna när den ökar. Alla analyserna är gjorda i simuleringsprogrammet Simulink. Resultaten kan appliceras när högspända likspänningsomvandlare vidareutvecklas för att skapa ett fungerande högspänt-likströms elnät som öppnar upp för en bredare användning av förnyelsebara energikällor.<br>Kandidatexjobb i elektroteknik 2020, KTH, Stockholm

Aujourd'hui l'evolution technologique constante des convertisseurs de puissance requiert une connaissance des composants de plus en plus approfondie. Les travaux presentes dans ce memoire de these concernent le tgb (igbt). On propose deux moyens d'analyse et de caracterisation differents, l'un experimental, l'autre utilisant une modelisation simplifiee ou douce. L'approche experimentale conduit a la realisation d'un veritable simulateur analogique dedie a l'electronique de puissance (saep). Il permet la maitrise et la variation independante de tous les parametres externes au tgb de maniere reproductible (commande, puissance et temperature). Il utilise l'auto-pilotage en courant et la strategie monocoup, la puissance installee etant quasi-nulle. La modelisation simplifiee ou douce des deplacements des charges permet une meilleure comprehension du comportement du tgb. Elle introduit les relations entre les phenomenes internes et les conditions externes avec la prise en compte des phenomenes physiques internes essentiels et la reduction du nombre de parametres physiques et structuraux. La mise en place de ces deux methodes a permis d'analyser le comportement du tgb en fonction des modes de commutation (dure et douce zv, zc) et de la commande de grille. Les resultats obtenus par ces deux approches complementaires donnent aux utilisateurs des informations autorisant une meilleure maitrise des tgb dans la conception des convertisseurs

Cette étude analyse la commutation de blocage d'un igbt utilise en commutation quasi-résonnante a zéro de courant. Deux igbt de structure technologique différente ont été étudiés, le premier est à base non homogène et a couche tampon, le second à base homogène et contrôlé d'injection de charges par l'émetteur. L'évolution de la charge stockée dans la base du transistor bipolaire interne au blocage est suivie et analysée à l'aide de simulations et d'expérimentations. Différents éléments interviennent sur l'évacuation de la charge stockée donc sur les pertes au blocage, qu'ils soient propres au composant (coefficients d'injection ou durées de vie) ou a sa commande (maintien du canal lors de la conduction de la diode antiparallèle). Ce qui permet de comprendre pourquoi les pertes au blocage sont plus faibles en commutation a zero de courant qu'en commutation commandée. Une caractérisation électrique et thermique de l'igbt permet ensuite de quantifier l'influence des conditions de commutation sur les pertes au blocage. Des limites de fonctionnement sont ainsi définies, pour s'affranchir de l'emballement thermique, principale cause de destruction des igbt a couche tampon en zcs a fréquence de découpage élevée

Aujourd'hui l'outil le plus utilisé par les spécialistes d'électronique de puissance est l'oscilloscope numérique. Tant que ces appareils sont utilisés pour vérifier le fonctionnement de circuits, leur précision est, généralement, suffisante. En revanche lorsqu'ils sont utilisés pour caractériser des interrupteurs de puissance, la précision nécessaire ne peut pas être atteinte directement. Les modes opératoires doivent être optimisés et les mesures doivent être corrigées pour obtenir une précision satisfaisante. La mise en place de ces corrections demande du temps et nécessite, souvent, l'utilisation d'un ordinateur. Il est bon, avant de les développer, de s'assurer de leur opportunité. Une première partie de ce travail est consacrée à l'étude des causes d'erreurs et à leur influence sur les résultats de mesure. Nous partons de mesures effectuées, avec les plus grands soins, sur un I. G. B. T. Et nous simulons, une à une, les sources d'erreur. Cette étude permet de tirer des critères de choix de matériel de mesure et de juger de la nécessité de certaines corrections. Dans une deuxième partie, nous nous intéressons à la modélisation de l'I. G. B. T. Et, plus généralement, des quadripôles électrostatiques non-linéaires. Par comparaison avec les mesures effectuées sur l'I. G. B. T. Nous montrons l'influence de la modélisation des capacités non-linéaires de l'I. G. B. T. Sur les résultats de simulation<br>Today, the main tool used by specialists in power electronics is the digital oscilloscope. As long as it is used to verify correctness of circuits working, its initial accuracy, generally, meets the needs. However, when fast power electronic switch characterization is at sake, required accuracy can't be directly reached. Operating modes must be optimized and corrections must be brought to measurement. Implementation of thèse corrections requires computer help and spends time. Before their development, it is good to be sure of their necessity. The aim of the first part of this work is to study causes of inaccuracy and their influence on measurement results. To do this, we take measurements with a maximum of care on an I. G. B. T. And we simulate, one by one, causes of errors. This study allows to détermine some références mark up to choice equipment or to judge the necessity of corrections. In a second part, we study the I. G. B. T. Modelling and, more generally, non-linear electrostatic four pôle modelling. By comparing measurements done on the I. G. B. T. With the results of simulation, we show influence of non-linear capacities of the I. G. B. T. On simulation

Demands for delivering high instantaneous power in a compressed form (pulse shape) have widely increased during recent decades. The flexible shapes with variable pulse specifications offered by pulsed power have made it a practical and effective supply method for an extensive range of applications. In particular, the release of basic subatomic particles (i.e. electron, proton and neutron) in an atom (ionization process) and the synthesizing of molecules to form ions or other molecules are among those reactions that necessitate large amount of instantaneous power. In addition to the decomposition process, there have recently been requests for pulsed power in other areas such as in the combination of molecules (i.e. fusion, material joining), gessoes radiations (i.e. electron beams, laser, and radar), explosions (i.e. concrete recycling), wastewater, exhausted gas, and material surface treatments. These pulses are widely employed in the silent discharge process in all types of materials (including gas, fluid and solid); in some cases, to form the plasma and consequently accelerate the associated process. Due to this fast growing demand for pulsed power in industrial and environmental applications, the exigency of having more efficient and flexible pulse modulators is now receiving greater consideration. Sensitive applications, such as plasma fusion and laser guns also require more precisely produced repetitive pulses with a higher quality. Many research studies are being conducted in different areas that need a flexible pulse modulator to vary pulse features to investigate the influence of these variations on the application. In addition, there is the need to prevent the waste of a considerable amount of energy caused by the arc phenomena that frequently occur after the plasma process. The control over power flow during the supply process is a critical skill that enables the pulse supply to halt the supply process at any stage. Different pulse modulators which utilise different accumulation techniques including Marx Generators (MG), Magnetic Pulse Compressors (MPC), Pulse Forming Networks (PFN) and Multistage Blumlein Lines (MBL) are currently employed to supply a wide range of applications. Gas/Magnetic switching technologies (such as spark gap and hydrogen thyratron) have conventionally been used as switching devices in pulse modulator structures because of their high voltage ratings and considerably low rising times. However, they also suffer from serious drawbacks such as, their low efficiency, reliability and repetition rate, and also their short life span. Being bulky, heavy and expensive are the other disadvantages associated with these devices. Recently developed solid-state switching technology is an appropriate substitution for these switching devices due to the benefits they bring to the pulse supplies. Besides being compact, efficient, reasonable and reliable, and having a long life span, their high frequency switching skill allows repetitive operation of pulsed power supply. The main concerns in using solid-state transistors are the voltage rating and the rising time of available switches that, in some cases, cannot satisfy the application’s requirements. However, there are several power electronics configurations and techniques that make solid-state utilisation feasible for high voltage pulse generation. Therefore, the design and development of novel methods and topologies with higher efficiency and flexibility for pulsed power generators have been considered as the main scope of this research work. This aim is pursued through several innovative proposals that can be classified under the following two principal objectives. • To innovate and develop novel solid-state based topologies for pulsed power generation • To improve available technologies that have the potential to accommodate solid-state technology by revising, reconfiguring and adjusting their structure and control algorithms. The quest to distinguish novel topologies for a proper pulsed power production was begun with a deep and through review of conventional pulse generators and useful power electronics topologies. As a result of this study, it appears that efficiency and flexibility are the most significant demands of plasma applications that have not been met by state-of-the-art methods. Many solid-state based configurations were considered and simulated in order to evaluate their potential to be utilised in the pulsed power area. Parts of this literature review are documented in Chapter 1 of this thesis. Current source topologies demonstrate valuable advantages in supplying the loads with capacitive characteristics such as plasma applications. To investigate the influence of switching transients associated with solid-state devices on rise time of pulses, simulation based studies have been undertaken. A variable current source is considered to pump different current levels to a capacitive load, and it was evident that dissimilar dv/dts are produced at the output. Thereby, transient effects on pulse rising time are denied regarding the evidence acquired from this examination. A detailed report of this study is given in Chapter 6 of this thesis. This study inspired the design of a solid-state based topology that take advantage of both current and voltage sources. A series of switch-resistor-capacitor units at the output splits the produced voltage to lower levels, so it can be shared by the switches. A smart but complicated switching strategy is also designed to discharge the residual energy after each supply cycle. To prevent reverse power flow and to reduce the complexity of the control algorithm in this system, the resistors in common paths of units are substituted with diode rectifiers (switch-diode-capacitor). This modification not only gives the feasibility of stopping the load supply process to the supplier at any stage (and consequently saving energy), but also enables the converter to operate in a two-stroke mode with asymmetrical capacitors. The components’ determination and exchanging energy calculations are accomplished with respect to application specifications and demands. Both topologies were simply modelled and simulation studies have been carried out with the simplified models. Experimental assessments were also executed on implemented hardware and the approaches verified the initial analysis. Reports on details of both converters are thoroughly discussed in Chapters 2 and 3 of the thesis. Conventional MGs have been recently modified to use solid-state transistors (i.e. Insulated gate bipolar transistors) instead of magnetic/gas switching devices. Resistive insulators previously used in their structures are substituted by diode rectifiers to adjust MGs for a proper voltage sharing. However, despite utilizing solid-state technology in MGs configurations, further design and control amendments can still be made to achieve an improved performance with fewer components. Considering a number of charging techniques, resonant phenomenon is adopted in a proposal to charge the capacitors. In addition to charging the capacitors at twice the input voltage, triggering switches at the moment at which the conducted current through switches is zero significantly reduces the switching losses. Another configuration is also introduced in this research for Marx topology based on commutation circuits that use a current source to charge the capacitors. According to this design, diode-capacitor units, each including two Marx stages, are connected in cascade through solid-state devices and aggregate the voltages across the capacitors to produce a high voltage pulse. The polarity of voltage across one capacitor in each unit is reversed in an intermediate mode by connecting the commutation circuit to the capacitor. The insulation of input side from load side is provided in this topology by disconnecting the load from the current source during the supply process. Furthermore, the number of required fast switching devices in both designs is reduced to half of the number used in a conventional MG; they are replaced with slower switches (such as Thyristors) that need simpler driving modules. In addition, the contributing switches in discharging paths are decreased to half; this decrease leads to a reduction in conduction losses. Associated models are simulated, and hardware tests are performed to verify the validity of proposed topologies. Chapters 4, 5 and 7 of the thesis present all relevant analysis and approaches according to these topologies.

碩士<br>國立東華大學<br>物理學系<br>106<br>The tellurium (Te) mico- and nano-structures were synthesized using tube furnace chemical vapor deposition (TFCVD). Then the mico- and nano-structures are annealed in TFCVD in order to produce the tellurium oxide (TeO2) mico- and nano-structures. The morphology of these Te and TeO2 mico- and nano-structures were studied using field-emission scanning electron microscopy (FESEM). The elemental information and electronic structure were revealed using energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The crystal structures were studied using X-ray diffractometry (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The various as-synthesized Te and TeO2 micro- and nano-structures were investigated with the electrical measurements of IV loops to probe the resistive switching properties at room temperature. We found only the TeO2 nanostructures of ~95 nm wide have the bipolar resistive switching properties, which are very potential to the application in random access memory (RRAM) devices.

碩士<br>國立東華大學<br>物理學系<br>104<br>Double-layers of nickel oxide/hafnium dioxides (NiO/HfO2) are synthesized on p-Si wafers using hot-filament metal oxide deposition technique. The thickness of the HfO2 thin films is controlled using the deposition time while the synthesis of NiO are kept same. The morphological feature and thickness of the thin films is observed using field-emission scanning electron microscopy (FESEM) equipped with the backscattering electron (BE) microscopy. The chemical compositions of the bi-layer NiO/HfO2 layer is confirmed using energy dispersive spectroscopy (EDS). Using X-ray diffractometry (XRD) we showed that thin films of NiO and HfO2 consists of cubic and monoclinic crystal structures, respectively. The resistive switching properties of the bi-layer NiO/HfO2 structures are studied using current-voltage sourcemeter. When the thickness of the HfO2 layer reduced to is ~40 nm, the NiO/HfO2 double layers shows an excellent resistive switching behavior. However, when the thickness of the HfO2 layer is over 40 nm, the resistive switching property does not exists. In addition, neither a thin film of single NiO nor HfO2 has the resistive switching characteristics, so it is indicative that the interface between the NiO layer and HfO2 layer plays a significant role by supplying a plenty of oxygen vacancies and hopping electrons.

碩士<br>國立聯合大學<br>電子工程學系碩士班<br>98<br>TiO2 films deposited by sol-gel method with two process variables are prepared to investigate the bipolar resistive switching (BRS) and unipolar resistive switching (URS) in metal/insulator/metal structure cells, and the difference between BRS and URS is the polarity of the on/off state transition voltage in the current-voltage curves. The first variable is the thermal treatment atmosphere in Ag/TiO2/Pt cells. The cells are URS in air atmosphere and BRS in oxygen atmosphere. The second variable is the bottom electrode materials of TiO2 cells, which are thermal treatment in air atmosphere. The cells are URS on Pt metal electrode and BRS on ITO oxide electrode. Compared with URS cells, BRS cells are lower in the operation voltage (BRS:1V < URS:2V) and current (BRS:10-3A < URS:10-2A), while higher in operation stability under multi-switching cycles (BRS:0.1V > URS:2.6V). Analyzing the IV curves in full-logarithmic plot, we find that by observing the fitting curves which show linear dependence (I?fV) at smaller voltage and the square one (I?fV2) at higher voltage, the carrier conduction mechanism concurs with space-charge-limited current theory. We infer that the critical factors for inducing URS or BRS could be the depth of traps in the film.

博士<br>國立成功大學<br>微電子工程研究所碩博士班<br>93<br>In this dissertation, we have successfully fabricated and demonstrated InP-based heterojunction bipolar transistors (HBTs). The characteristics of InP/InGaAs HBT with a superlattice-collector (SC) structure and InGaAs/InGaAsP composite-collector HBT (CCHBT) are measured and discussed. In addition, two interesting optoelectric switches, a double-barrier-emitter triangular-barrier optoelectronic switch (DTOS) and a bulk-barrier optoelectronic switch (BBOS) with an AlGaAs/δ(n+)-doped sheet/GaAs/InAlGaP collector structure are also investigated and discussed. 　The studied devices were grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD) and molecular beam epitaxy (MBE). The characteristics of epitaxial layers will be analyzed by double-crystal x-ray diffraction (DCXRD), photoluminescence (PL), and electrochemical CV profiling (ECV). After finishing the growth, mesa-type devices were formed by utilizing photolithography, vacuum evaporation, lift-off, alloying and selective etching techniques. 　DC characteristics of an interesting InP/InGaAs heterojunction bipolar transistor with a superlattice (SL) structure incorporated in the base-collector (B-C) junction are demonstrated. In the SL structure, holes injected from the collector collide with holes confined in the SL and impact them out of the SL across the valence-band discontinuities. With a collector-emitter (C-E) voltage VCE less than the C-E breakdown voltage BVCEO, the current gain can be increased at base-current inputs because the released holes from the SL inject into the base to cause the E-B junction operating under more forward-biased condition. An AC current gain up to 204 is obtained. At B-E voltage VBE inputs, the released holes travel to the base terminal to decrease the base current. The studied HBT exhibits common-emitter current gains exceeding 47 at low current levels and useful gains spreading over 7 orders of magnitude of collector current. DC characteristics of an interesting HBT with an InGaAs/InGaAsP composite-collector (CC) structure are studied and reported. Due to the insertion of an InGaAsP setback layer at the base-emitter (B-E) heterojunction, the potential spikes as well as the electron blocking effect are suppressed significantly. In addition, the presence of an effective base-collector (B-C) homojunction can substantially reduce the current blocking effect. The studied device gives impressed dc performance including small offset and saturation voltages without degrading the breakdown behaviors. The typical dc current gain of 118 and the desired current amplification over 11 decades of magnitude of collector current IC are obtained. 　On the other hand, a triangular-barrier and a double-barrier structure are combined to form a double-barrier-emitter triangular-barrier optoelectronic switch (DTOS). In the structure center of the triangular barrier, a p-type delta-doped quantum well is inserted to enhance the hole confinement. Owing to the resonant tunneling through the double-barrier structure and avalanche multiplication in the reverse-biased junction, N-shaped and S-shaped negative-differential-resistance (NDR) phenomena occur in the current-voltage (I-V) characteristics under normal and reverse operation modes, respectively. The NDR characteristics show variations from dark to illumination condition. Temperature effects on the NDRs of the DTOS are also obvious. The illumination and temperature influences on the device characteristics are investigated. 　Two-terminal switching performances are observed in a new bulk-barrier optoelectronic switch (BBOS) with an AlGaAs/δ(n+)/GaAs/InAlGaP collector structure. The device shows that the switching action takes place from a low current state to a high current state through a region of NDR. The transition from either state to the other may be induced by an appropriate optical or electrical input. It is seen that the effect of illumination increases the switching voltage VS, holding voltage VH, holding current IH and decreases the switching current IS, which is quite different from other reported results. In addition, it possesses obvious NDR even up to 435K. This high-temperature performance provides the studied device with potential high-temperature applications.

碩士<br>長庚大學<br>電子工程學系<br>104<br>In this thesis, bipolar resistive switching (BRS) characteristics using W/SiO2/TiN and Ir/SiO2/TiN RRAM structure have been investigated. Complementary resistive switching (CRS) using Ir/SiO2/TiN single cell has also been demonstrated. Defective SiO2 switching material is confirmed by X-ray photoelectron spectroscopy. Typical BRS are shown in W/SiO2/TiN stack at the current compliances of 500 µA and 200 µA. Statistical analysis is done by taking randomly 50 devices which confirm that device-to-device switching uniformity is ˃ 75%. In case of W/SiO2/TiN, the low resistance state (LRS) current shows Ohmic conduction, and high resistance state (HRS) current shows Schottky emission at low field and hopping conduction at higher field. On the other hand, both HRS and LRS show Ohmic conduction at low field, and hoping conduction is observed at higher field by using Ir/SiO2/TiN structure. The SiO2 thickness based BRS characteristics have been explained. In addition, good data retention of > 3hr and long read endurance of >106 cycles with a small pulse width of 1µs are observed. Resistive switching mechanism using W and Ir electrode is explained by oxygen ions migration under external bias has been explained by schematic model. The CRS is observed by tuning proper bias in Ir/SiO2/TiN single cell without metal interlayer. In CRS, low field and high field regimes are complied with space-charge limited current (SCLC) and Fowler-Nordheim (F-N) tunneling mechanism, respectively. The CRS mechanism has been explained considering oxygen ions migration or vacancy (VO) mediated filamentary schematic model. Superior read endurance of ˃104 cycles is obtained at small pulse width of 1 µs with acceptable resistance ratio of ~10. The non-linearity factor of >10 is also obtained, which is useful for future three-dimensional (3D) crossbar memory applications.

碩士<br>國立清華大學<br>電子工程研究所<br>99<br>In this thesis, we discuss on the top electrode effect, current conduction mechanism and annealing effect for the HfO2 based RRAM. At the discussion of the top electrode effect, the W top electrode causes the device to present unipolar operation, but in the W/Ti top electrode present bipolar operation. We may know that top electrode influence the switching characteristic and the polarity of RRAM seriously. Second, the W/Ti/HfO2/TiN device in LRS is the ohmic conduction, but when HRS, the low voltage region (＜0.05V) is the ohmic conduction, the high voltage region (＞0.1V) is Poole-Frenkel emission. Finally, in the annealing effect, the suitable temperature condition to obtain the 10 times of promotion in endurance. From the result of the annealing effect, we can provide a method to improve endurance and have the development potential.

碩士<br>東海大學<br>電機工程學系<br>100<br>In this paper we present the design and through the TSMC 0.25μm HV process to achieve a single-phase bipolar voltage switching DC-AC inverter. The design of the main structure is PWM bipolar switching technology and a level shift circuit connect to full-bridge circuit to do the DC input voltage to the AC output voltage control. A supply voltage and temperature-independent bandgap reference circuit is used in the inverter that has a output voltage of 9.4V/60Hz of sine wave. The AC sine wave voltage is provided to a small AC LED load. The chip area is 1.9 x 2.05mm2. Circuit simulation verifies the performance and feasibility of the conversion system.

In den Manganaten können kleine Änderungen von externen Feldern die elektronischen, magnetischen und strukturellen Eigenschaften drastisch beeinflussen. In dieser Arbeit wird der Einfluss von elektrischen Feldern und Licht auf den elektrischen Transport in Manganatschichten analysiert. Durch elektrische Feldern können die Widerstände des Manganats remanent und reversibel zwischen verschiedenen Widerstandsniveaus in Abhängigkeit von der Polarität und der Größe des elektrischen Feldes eingestellt werden. Dieser, auch als bipolares Widerstandsschalten bezeichnete Effekt, wird in nanokolumnaren Lanthan und Strontium dotierten Manganatschichten mittels leitfähiger Rasterkraftmikroskopie und in mittels Elektronenstrahllithographie präparierten Mikrostrukturen studiert. Des Weiteren wird der Einfluss von Laseranregungen auf die erste und dritte harmonische Spannung in einer Lanthan und Barium dotierten Manganatschicht untersucht.

碩士<br>國立成功大學<br>材料科學及工程學系<br>103<br>Abstract In this study, the resistance switching mechanisms of Ta/TaOx/Pt and Ta/TaOx/ITO devices are explored based on I-V sweeping curves, characteristic impedance and material characteristics. First, TEM is used to investigate the thickness of the device and crystallinity of the TaOx films. Chemical bonding state in TaOx active layer is observed with XPS. Second, regarding to electrical properties of TaOx-based device, we not only use precision semiconductor parameter analyzer (Agilent 4156C) to get the resistive switching curve of TaOx-based device, but also use the precision impedance analyzer (Agilent 4294A)to get the characteristic impedance of TaOx-based device at different states and different dc bias. The first part of this dissertation is about material characteristics of TaOx TEM, analysis reveals that TaOx is amorphous. Second, from the result of XPS, the chemical states of Ta(+0) and Ta(+5) are coexist near Ta/TaOx interface, so we can conclude that there is a oxygen vacancy-rich region, the Transition Region (TR), exist near Ta/TaOx interface. The second part of this study is about electrical properties of TaOx-based devices. From resistive switching curves, both Ta/TaOx/Pt and Ta/TaOx/ITO devices can be operated in bipolar mode, with writing at positive bias and erasing at negative bias. The characteristic impedance at high and low resistance states of the two devices can be fitted with Rs-R//C model, and the value of R at high resistance state (HRS) is higher than at low resistance state (LRS) for both devices, which means that during the resistance-switching process, oxygen vacancies will be driven by different polarity bias to form or rupture the conductive filament. In the third part of this study, we measure the impedance under positive and negative dc bias to observe the characteristic impedance during set and reset process. From the result of positive dc bias impedance measurement on the HRS devices, we found that the equilibrium circuit of the two devices will be first changed from Rs-R//C model into a complex model involving inductors, then turn back to Rs-R//C after removing positive bias. In the meaning time, the R changes from the initially high value to a low value, which means that the conductive filament will be formed and the shape of the filament will be changed during positive dc bias operation. From the result of negative dc bias impedance measurement on the LRS devices, the equilibrium circuit of the two devices will approximately maintain Rs-R//C, and the value of R for two devices is gradually become larger during negative biased impedance measurement, which means that the conductive filament in active layer will be ruptured during negative dc bias operation. Regarding the differences of using Pt and ITO bottom electrodes is that, ITO bottom electrode will absorb or release oxygen vacancies during resistance switching process, which may affect the resistance-switching process, however, Pt bottom electrode will not. So from the experiment, we can found that several difference between Ta/TaOx/Pt device and Ta/TaOx/ITO device. First, in high resistance state (HRS), the value of R fitted from Rs-R//C model in Ta/TaOx/Pt device is larger than Ta/TaOx/ITO device, however, in low resistance state (LRS) , the value of R fitted from Rs-R//C model in Ta/TaOx/Pt device is smaller than Ta/TaOx/ITO device. Second, the two electrical parameters of Vset and on/off ratio, which get from characteristic resistive switching curve, both in Ta/TaOx/Pt device are larger than in Ta/TaOx/ITO device. Summary The resistive switching process in oxide-based RRAM is generally originated from the formation-and-rupture of conductive filament via oxygen vacancies. However, to observe the filament evolution during resistive switching process is difficult. In our study, we measure impedance of RRAM at different resistance states to study the filament evolution during resistive switching. Two TaOx-based resistive switching memories, Ta/TaOx/Pt and Ta/TaOx/ITO devices are investigated in this work. First, from the material analysis, we have found an oxygen vacancy rich region, the transition region, existing near Ta/TaOx interface. Secondly, from the analysis of impedance at different states for two devices, we can find that the impedance at different states all can be fitted with Rs-R//C circuit model, and the value of R for two devices in high resistance state is substantially larger than in low resistance state, which is the evidence to show that the filament rupture or formation during resistive switching process.

Resistive random access memory (RRAM) is a non-volatile memory technology based on resistive switching in a dielectric or semiconductor sandwiched between two different metals. Also known as memristors, these devices are potential candidates for a next-generation replacement for flash memory. In this thesis, bipolar resistive switching is reported for the first time in solution-deposited zinc-tin-oxide (ZTO). The impact of the compliance current on device operation, including the SET and RESET voltages, pre-SET, RESET and post-RESET currents, the resistance ratio between the low and high resistance states, retention, and the endurance, is investigated for an isolated Al dot/ZTO/Ir blanket device and for Al/ZTO/Pt crossbar RRAM devices. A gradual forming process is devised to improve device stability and performance. It is found that the device performance depends critically on the compliance current density that is used to limit the breakdown conduction during the SET operation. In addition, it was found that the conduction and switching mechanisms are consistent with the filament model of formation and rupture of conductive filaments.<br>Graduation date: 2012

碩士<br>國立清華大學<br>電子工程研究所<br>88<br>Electron Irradiation is a technique used to control the Insulated Gate Bipolar Transistor (IGBT) switching performance. It can reduce the minority carrier lifetime and increase the recombination rate of the excess minority carriers by generating the atomic displacement and trap centers in the drift region of the IGBTs. However, electron irradiation induces undesired effects on other parameters, such as forward voltage drop and threshold voltage. In this thesis, we design a series of electron irradiation dosage to optimize the steady states and switching performance of IGBTs considering various design parameters. Then, the model of predicting turn-off time is created by two-dimensional simulator MEDICI and circuit simulator HSPICE. Finally, We have successful fabricated IGBT with 600V breakdown voltage, 10A on-current, 2.49V on-state voltage drop at 10A, and high speed, 365nsec turn-off time.

博士<br>國立成功大學<br>電機工程學系<br>89<br>In this dissertation, we have successfully fabricated and demonstrated InP-based heterojunction bipolar transistors (HBT's). The characteristics of InGaAs/InP superlattice emitter resonant tunneling bipolar transistors (SE-RTBT's) and InGaAlAs/InP d-doped HBT's are measured and discussed. The characteristics of epitaxial layers and SiO2 film will be analyzed by double-crystal x-ray diffraction (DCXRD), photoluminescence (PL), energy dispersive x-ray spectrometer (EDS), and Auger electron spectroscopy (AES). The scanning electron microscope (SEM) technique shows the top view and cross section of the studied devices. In addition, DC and RF heterojunction bipolar transistor (HBT) fabrication process are illustrated. The transfer length method (TLM) measurement is used to calculate the resistance of each ohmic contact layers. Two different SE-RTBT's are reported. The device A contains a 5-period superlattice and 800A emitter layer. In addition, a 3-period superlattice and 150A emitter are included for device B. AC common emitter current gain up to 170 and 54 are obtained for device A and B, respectively. The current gains are reduced about 6% and 7.4% for both devices as the temperature is decreased from 300K to 77K. The resonant tunneling effect is observed at 77K for device A. Due to the use of superlattice and critical-designed emitter, the DC performance is improved and more stable temperature-dependent characteristics is achieved. By using InP emitter ledge, DC current gain of the devices can be enhanced. The unit current gain cutoff frequency fT of 12GHz and 15GHz for device A and B are obtained, respectively. Power characteristics and noise performance are also illustrated. A narrow base d-doped InGaAlAs/InP negative-differential-resistance (NDR) HBT is proposed in this thesis. The AC common-emitter current gain up to 22 is obtained. For the different controlled base current ( IB=2uA/step, 10uA/step, 100uA/step ), the different topee-shaped, N-shaped, and conventional characteristics of HBT's are observed. The peak-to-valley-current ratio (PVCR) up to 11 is obtained. The mechanism is considered to be the modulation of potential spike due to the base resistance effect on the emitter injection efficiency. Besides, multiple S-shaped NDR phenomena are also observed under the inverted operation mode. This is due to the avalanche multiplication and two-stage barrier lowering effect. Optical characteristics of the studied NDR-HBT show that a photocurrent up to 1.01mA is obtained. On the other hand, a new multiple-state and optically controllable optoelectronic switch based on an InGaAlAs/InP -doped HBT structure is demonstrated. Common-emitter current gain up to 25 is obtained as the device is operated under forward operation mode. However, a significant S-shaped NDR phenomenon is found under the applied reverse-biased voltage. The second-route S-shaped NDR phenomenon is observed under illumination without changing the bias condition. The multiple-route and multiple-step current-voltage (I-V) characteristics at 77K are also observed. The novel MNDR I-V characteristics are attributed to the avalanche multiplication, successive two-stage barrier lowering process and electron confinement effect in the InGaAs quantum well. Experimental results reveal that the studied device can be operated among a wide temperature range. Table Captions Figure Captions Chapter 1. Introduction 1.1. Brief history of heterojunction bipolar transistors (HBT's) 1.2. Advantages of InGa(Al)As/InP over AlGaAs/GaAs or InGaP/GaAs 1.3. Dissertation objective Chapter 2. Material Growth and Device Fabrication 2.1. Introduction 2.2. MOCVD system 2.3. Growth conditions and characteristics of InP and InGa(Al)As 2.4. A.C. sputtering system and characteristics of SiO2 film 2.5. HBT fabrication process 2.5.1. D.C. and R.F. layout design 2.5.2. Emitter, base, and collector definition 2.5.3. Selective etching and device isolation 2.5.4. SiO2 growth and interconnection 2.5.5. Transfer length method (TLM) ohmic contact measurement 2.6. Summary Chapter 3.InGaAs/InP Superlattice Emitter Resonant Tunneling Bipolar Transistors (SE-RTBT's) 3.1. Introduction 3.2. Layer structures of 54 and 32 SE-RTBT's 3.3. Theoretical analyses of emitter thickness and superlattice layers 3.4. Theoretical analyses of high frequency performance 3.5. Experimental results and discussion 3.5.1. Advantages of superlattice and InP emitter layers 3.5.2. D.C. and temperature dependent characteristics of SE-RTBT's 3.5.3. Performance of InP emitter ledge 3.5.4. Influence of SiO2 on the device characteristics 3.5.5. RF characteristics of SE-RTBT's 3.6. Summary Chapter 4. InGaAlAs/InP Delta-Doped Negative-Differential-Resistance Heterojunction Bipolar Transistor (NDR-HBT) 4.1. Introduction 4.2. Layer structure of NDR-HBT 4.3. Experimental results and discussion 4.3.1. Influence of delta-doped sheet on the potential spike 4.3.2. D.C. characteristics and photonic-sensitive performance of NDR-HBT 4.3.3. Mechanism of NDR-HBT 4.3.4. Circuit applications of NDR-HBT 4.4. Summary Chapter 5. InGaAlAs/InP Multiple-Negative-Differential-Resistance (MNDR) Switching Device with HBT Structure 5.1. Introduction 5.2. Layer structure of MNDR switching device 5.3. Experimental results and discussion 5.3.1. D.C. and temperature characteristics of MNDR device 5.3.2. Mechanism of MNDR switching device 5.3.3. Circuit applications of MNDR switching device 5.4. Summary Chapter 6. Conclusion and Prospect 6.1. Achievement 6.2. Future work References Publication List Vita

碩士<br>國立交通大學<br>電子工程系所<br>97<br>In this thesis, the RRAM devices manufactured based on SrZrO3 (SZO) thin films are studied and developed.　At first, we will introduce the applications, fundamental characteristics, and advantages of next-generation nonvolatile memories. The conduction mechanisms of RRAM that have been published are also discussed.　In experimental details, Pure SZO film was deposited on the LaNiO3 buffer layer by RF magnetron sputter. Pt and Ti act as bottom and top electrode by Dual E-Gun evaporation, respectively. Therefore, electrode/resistive thin film/buffer layer/electrode structure is formed. In the beginning, we will discuss the influence of various top-electrode metals for SZO thin film devices. The switching property, endurance and device yield could be stabilized and enhanced by Ti top electrode. Secondly, we use the post metal annealing (PMA) treatment on Ti/SZO structure to generate TiOx interface layer could reduce the operation voltages and also enhance the endurance and device yield of memory device. The SZO memory device with Ti top electrode has the better and stable resistive switching characteristic by PMA at 200℃ for 1 hour. The effects of resistive switching property by different PMA temperatures are also compared and discussed. We conjecture that TiOx interface layer between Ti and SZO film by PMA at 200℃ has good influence on resistive switching property by experiment and proofs.

碩士<br>國立臺灣科技大學<br>材料科學與工程系<br>100<br>A thin copper-doped tantalum oxide (Cu-TaOx) film was prepared by plasma oxidation of a copper-doped tantalum nitride (Cu-TaN), and its resistance switching behavior was studied. A Cu-TaN film was firstly deposited by co-sputtering as a bottom electrode, then the Cu-TaN film was oxidized in an oxygen-containing plasma to form an insulating layer (Cu-TaOx). At last, the TaN film was deposited on top of the insulating layer as the top electrode to form a MIM structure. The insulating layer was fabricated by RF plasma oxidation and microwave plasma oxidation, respectively. Both of these two devices exhibited bipolar resistance switching when DC voltages were swept. And the resistance ratio of RHRS/RLRS measured at +0.3 V were above 10 to 100 using two different compliant currents. This phenomenon suggested that conducting filamentary paths may form inside the Cu-TaOx layer. In the microwave plasma oxidation, the device showed Schottky emission in the low voltage region of HRS, and exhibited poole-frenkel emission in the high voltage region of HRS, whereas LRS followed SCLC mechanism. In the contrast, when the insulating layer was formed by RF plasma oxidation, the device showed SCLC mechanism in HRS and Ohmic contact in LRS, respectively. The insulating layers made by two different oxidization methods were examined by XPS, SEM and TEM. Different compositions and structures were revealed in the insulating layer, causing different conducting mechanism in the I-V analysis.

碩士<br>國立臺灣科技大學<br>材料科學與工程系<br>102<br>In this study, we used titanium (Ti) and indium tin oxide (ITO) as the eletrodes to fabricate the TiN/Ti/TiOx/ITO and ITO/TiOx/Ti/TiN resistance random acess memory (RRAM) without depositing a resistor layer. It was found that an interfacial-oxide layer TiOx was spontaneously formed between Ti and ITO layers. The TiN/Ti/TiOx/ITO device showed bipolar switching of resistance in counterclockwise direction without forming a process. The TiN/Ti/TiOx/ITO device changed from high resistive state (HRS) to low resistive state (LRS) at about 1.16 V and changed back to HRS at about -1.00 V. The endurance test showed resistance ratio, RHRS/RLRS, for TiN/Ti/TiOx/ITO device was 8, and the DC voltage sweeps could achieve about 500 cycles at room temperature. The conducting mechanism for TiN/Ti/TiOx/ITO device followed Ohmic cconduction at LRS. And the HRS also followed Ohmic cconduction at low voltage, but Poole-Frenkel emission at high voltage. Furthermore, the area-dependence characteristic of resistance for the TiN/Ti/TiOx/ITO device was constant at LRS, but decreased with increased areas at HRS. And the characteristic of resistance was increased with temperatures for the TiN/Ti/TiOx/ITO device at LRS and HRS. Filamentary path of oxygen vacancies was suggested to dominate the conduction in the TiN/Ti/TiOx/ITO device. The ITO/TiOx/Ti/TiN device also showed bipolar switching of resistance but in clockwise direction without a forming process. And the ITO/TiOx/Ti/TiN device could be reset from LRS to HRS at about 2.0 V and set back to LRS at about -1.4 V. Furthermore, the resistance ratio, RHRS/RLRS, was around 1.5 and unstable for the ITO/TiOx/Ti/TiN device. After switching stably, the conducting mechanism of ITO/TiOx/Ti/TiN device followed Ohmic cconduction at LRS, but combined Ohmic at low voltages and space-charge-limited conduction at high voltages at HRS. By annealing it in vacuum at 250 ℃ for 30 min, the ITO/TiOx/Ti/TiN device had stable switching behavior.

碩士<br>國立臺灣大學<br>應用物理所<br>101<br>The growth and bipolar resistive switching behavior of ZnO nanorods / CuO PN heterojunction are reported in this thesis. ZnO nanorods were grown on ITO substrate by using hydrothermal method. A Cu layer was then grown on top of the ZnO nanorods and oxidized to become CuO, but before the growth of the Cu layer, the empty spaces between nanorods were filled with photo-resist to prevent current leakage. Scanning electron microscope, Photoluminescence and X-Ray diffraction were used to study the surface morphology and the crystalline structure of the sample and the results indicate that the sample have good crystalline quality and optical properties. Typical PN junction rectifying behavior was observed for the sample in the current- voltage measurement. After the forming process, the bipolar switching behavior can be clearly observed with a high/low ratio of about 10 between high resistance state and low resistance state. The operation current is very low in our device, and it can be operated at a current level of 10-7 A. In additions, current self- compliance is observed in both the set and reset processes; the current in the device decreases in both the set and rest processes. Several different kinds of electrodes were deposited on the samples to study the effect of the electrodes on the switching behavior of the devices, and the results indicate that the switching behavior is electrode-independent. A model which takes into account of the migration of vacancies in the depletion region is proposed and can explain successfully the observed experimental results.

碩士<br>國立臺灣科技大學<br>材料科學與工程系<br>101<br>In this study, we demonstrate the effect of interfacial aluminum oxide (AlOz) layer near the Al-TaOxNy interface and compare reversible switching behaviors of the Al/TaOxNy/TaN and TaN/TaOxNy/Al resistance random access memory (RRAM) devices. The TaN and Al films which are compatible with the integrated circuits technology were prepared by sputter deposition as the electrode layers to replace expensive Pt electrode, and the tantalum oxynitride (TaOxNy) film was prepared by reactive sputtering or microwave plasma oxidation of the TaN films as the insulating layer. The resistance swiching operation was unstable for the Al/TaOxNy/TaN devices whose TaOxNy films were prepared by reactive sputtering or microwave plasma oxidation, and the resistance of HRS and LRS increased with increased resistance switching cycles. In comparison, the switching behavior of TaN/TaOxNy/Al device whose TaOxNy film was prepared by reactive sputtering exhibited good stability. The resistance ratio of RHRS/RLRS measured at -0.2 V of the TaN/TaOxNy/Al device was about 2.5, and the numbers of resistance switching could be up to 1000 cycles at room temperature. On the mechanism analysis of TaN/TaOxNy/Al device, HRS were the Ohmic conduction at the low operation voltages and the Poole-Frenkel emission at high operation voltages, respectively, and LRS was the Ohmic conduction. To elucidate the conduction mechanism, we carried out electrical measurements of the RRAM with different cell areas and at various temperatures. The TaN/TaOxNy/Al device in LRS had constant resistance with increased cell’s area and decreased resistance with increased temperature. It suggests that the electron transport is probably attributed to oxygen vacancies in conduction filaments.

碩士<br>明新科技大學<br>電子工程系碩士班<br>106<br>Abstract Insulated Gate Bipolar Transistor (IGBT) is a popular power discrete device. The gate voltage of the MOSFET controls the high input impedance of the transistor, and it also uses the BJT's double-loaded sub-stream to achieve high current and low on-voltage control performances. By the way, IGBTs can also work with high reverse bias and is thus considered the prime power discrete. However, in order to understand the electrical performances of IGBT, some alternative measuring tool is used to do the job because high power curve tracer is not always available. In this study, devices of different device structures (including different gate widths and source widths) with different processes are fabricated and measured. The author analyzes the switching function to conclude the performances of the devices. The comparisons give the clues on the size design for the layout corresponding to the selected process conditions. On the other hand, 3-D PFinFET devices are put to measurement. The traditional current-voltage characteristic formula is modified and the modified one is used to fit measured I-V curves. At higher VG, the leakage current is ignorable and the fitting curves can reasonably fit the I-V curves. But for VG = 0.0V, it becomes mandatory that the leakage term, which is proportional to the difference of Gate and Drain biases, should be taken into account to appropriately fit the curves.

Memristor, defined as a two-terminal device which exhibits a pinched hysteresis loop in the current-voltage characteristics, is a main component of the resistive random access memory. Both memristor and memristive phenomena, known also as resistive switching (RS), have been thoroughly investigated in the past nearly two decades. This dissertation investigates YMnO3 thin films and explores a new concept concerning utilization of multiferroic properties for activation and/or enhancement of RS. It is hypothesized that the charged domain walls and/or vortex cores in YMnO3 thin films can act as an effective nanoscale features which support formation of the conductive filaments and, in consequence, enable development of an electroforming-free memristive structure. Results of the electrical characterization of YMnO3-based metal-insulator-metal structures indicate that hexagonal YMnO3 films deposited on metal-coated oxide substrate exhibit electroforming-free unipolar resistive switching (URS) while orthorhombic YMnO3 films grown on the doped oxide substrate show bipolar resistive switching (BRS). Observed URS is assigned to the formation and rupture of conductive, metallic-like filaments induced by the thermo-chemical phenomena. Results of polarity-dependent studies reveal that formation of conductive filaments proceeds in the electrostatic discharge event which is followed by their irreversible rupture during the reset process. Main properties of the observed URS include very good retention of programmed states, large memory window (between 10E+2 and 10E+4), high voltage and current required for set and reset, respectively, and low endurance. BRS is attributed to the complementary electronic and ionic processes within the p-n junction formed at the interface between p-YMnO3 and n-type oxide substrate. Results of ferroelectric characterization reveal that resistively switching YMnO3 films do not exhibit ferroelectric properties. Therefore, observed RS in YMnO3-based structures can not be directly related to the presence of charged domain walls and/or multiferroic vortex cores. Prospective functionality extension of YMnO3-based memristive devices is developed and presented on the example of photodetecting properties of metal-YMnO3-insulator-semiconductor stacks. Studies conducted within the framework of this doctoral dissertation investigate the resistive switching behaviour of YMnO3-based junctions. Obtained results contribute to the better understanding of the resistive switching and failure mechanisms in ternary oxides, and provide hints toward device engineering.<br>Der Memristor ist definiert als eine Zweipol-Vorrichtung, die eine hysteretische Strom-Spannungs-Charakteristik aufweist. Memristoren sind nichtflüchtige Widerstandsspeicher, deren elektrischer Widerstand mittels elektrischer Spannungspulse verändert werden kann. Sowohl Memristoren als auch memristive Widerstandsschalter (RS) werden seit mehr als zwei Jahrzehnten intensiv untersucht. Diese Dissertation untersucht YMnO3-Dünnschichten mit zirkularen Vorderseiten-Elektroden und unstrukturierten Rückseiten-Elektroden und erforscht ein neues Konzept über die Nutzung der multiferroischen Eigenschaften für die Aktivierung und/oder Verbesserung des memristiven Verhaltens. Es wird angenommen, dass die geladenen Domänenwände und/oder Vortices in YMnO3-Dünnschichten die Bildung leitfähiger Filamente wirksam unterstützt und folglich die Entwicklung eines neuartigen, formierungs-freiem Widerstandsspeichersermöglicht. Die Ergebnisse der elektrischen Charakterisierung von YMnO3-basierten Widerstandsschalter zeigen unipolares RS (URS), wenn eine metallische Rückseitenelektrode verwendet wird und bipolares RS (BRS), wenn als Rückseitenelektrode ein metallisch leitendes Oxid-Substrat verwendet werden. Das URS wird als thermochemisches RS klassifiziert und mit der Bildung und Auflösung metallisch leitender Filamente korreliert. Das BRS wird auf das Einfangen/Freigeben von Defekten in der Raumladungszone des YMnO3 im pn-Übergang von p-YMnO3/n-Nb:SrTiO3-Strukturen zurückgeführt. Die wichtigsten Eigenschaften des formierungsfreien URS sind die sehr gute Retention der programmiertenWiderstandszustände, große Speicherfenster (zwischen 10E+2 und 10E+4), die hohe Schreibspannung für den Set-Prozess und der hohe Schreibstrom für den Reset-Prozess. Die Endurance ist aufgrund der Degradation des Vorderseiten-Elektrode gering. Die Ergebnisse des polaritätsabhängigen Widerstandsschaltens zeigen, dass der Set-Prozess mit elektrostatischer Entladung einhergeht. Die ferroelektrische Charakterisierung zeigt, dass die YMnO3–Dünnfilme keine ferroelektrischen Eigenschaften aufweisen. Daher kann das beobachtete URS nicht direkt auf die Anwesenheit von geladenen Domänenwände und Vortices zurückgeführt werden. Darüberhinaus wurden die photodetektierenden Eigenschaften von Metall-YMnO3-Isulator-Halbleiter-Stacks als potenzielle Erweiterung der Funktionalität von YMnO3-basierten memristiven Bauelementen vorgestellt und vorgeschlagen. Im Rahmen der vorliegenden Dissertation wurde das Widerstandsschalten von multiferroischen, YMnO3-basierten Widerstandsschaltern untersucht. Die erhaltenen Ergebnisse tragen zu einem besseren Verständnis des Widerstandsschaltens von multiferroischen Materialien bei.

This work aims to characterize Indium-Gallium-Zinc-Oxide nanoparticles (IGZOnp) as a resistive switching matrix in metal-insulator-metal (MIM) structures for memristor application. IGZOnp was produced by low cost solution-based process and deposited by spin-coating technique. Several top and bottom electrodes combinations, including IZO, Pt, Au, Ti, Ag were investigated to evaluate memory performance, yield and switching properties. The effect of ambient and annealing temperature using 350 ºC and 200 ºC was also analysed in order to get more insight into resistive switching mechanism. The Ag/IGZOnp/Ti memristor structure annealed at 200 ºC exhibits the best results with a large yield. The device shows a self-compliant bipolar resistive switching behavior. The switching event is achieved by the set/reset voltages of -1 V/+1 V respectively with an operating window of 10, and it can be programmed for more than 100 endurance cycles. The retention time of on and off-states is up to 104 s. The obtained results suggest that Ag/IGZOnp/Ti structure could be applied in system on a panel (SoP) as a viable device.