Dissertations / Theses on the topic 'GaN'
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Tourret, Julie. "Etude de l'épitaxie sélective de GaN/saphir et GaN/GaN-MOVPE par HVPE." Clermont-Ferrand 2, 2008. http://www.theses.fr/2008CLF21887.
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Le nitrure de gallium (GaN) est un matériau en plein essor depuis le début des années 1990 pour des applications dans le domaine de l'optoélectronique telles que les diodes électroluminescentes (DELs) bleues ou blanches, les diodes lasers (DLs) bleues ou les détecteurs ultra-violets. L'activité épitaxie de GaN par la technique de croissance HVPE (Epitaxie en phase vapeur par la méthode aux hydrures), a vu le jour au LASMEA en 1998. Les premières études expérimentales et de modélisation réalisées sur des échantillons de faibles dimensions (surface d'environ 1 à 3 cm2) ont conduit à la mise en évidence des mécanismes de croissance et à la maîtrise du procédé. Le développement de ce matériau à l'échelle industrielle a nécessité de travailler sur des surfaces de dimension plus grandes de l'ordre de deux pouces. Un nouveau dispositif expérimantal HVPE a été conçu dans ce sens, mis en place au sein du laboratoire et le procédé a été validé. De nouvelles investigations ont été menées sur l'étude de l'épitaxie sélective de GaN pour la réalisation de structures périodiques de faible dimensionnalité à morphologies contrôlées. Des structures de morphologies poutres et pyramidales de GaN de 1 à 2 µm de large ont ainsi pu être épitaxiées par la technique HVPE. Une analyse systématique de la variation des conditions de croissance est effectuée, visant à maîtriser l'ensemble des paramètres qui influent sur les morphologies et les dimensions des structures. Cette étude est couplée à la compréhension des mécanismes de croissance mis en jeu au cours de l'épitaxie sélective de GaN
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Ganz, Philipp Ralph [Verfasser], and H. [Akademischer Betreuer] Kalt. "Wachstum und Charakterisierung von Cu-dotiertem GaN und GaN auf MgF2 / Philipp Ralph Ganz. Betreuer: H. Kalt." Karlsruhe : KIT-Bibliothek, 2012. http://d-nb.info/1034404814/34.
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Karlsson, Alexander, and Alexander Vestlund. "Integrated Multiband High Gain and Stable GaN Input Matching Network." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-128423.
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This bachelor thesis covers the basics of constructing a stable transistor based amplifying circuit. The task was to design an input match in order to increase the gain of a specific transistor. This transistor model, GH60015D is developed by Cree Inc. When this transistor is stabilized much of the original gain is reduced. The main problem is that it fails to deliver high amounts of gain over a wide band while remaining stable. To counter this, an input match with multiband purposes is designed in order to increase the gain over specific frequency bands. The thesis covers the basics to design an input matching network for a transistor and how one can analyze circuits in more detail in order to get as a realistic simulation as possible. In this project ADS software and models of the CH60015D are used in order to simulate circuits intended for implementation that is meant to be built on a glass-substrate. The desired result of the work is to obtain as much large signal gain as possible over the frequency bands 2.11-2.17GHz and 2.62-2.69GHz while maintaining stability. The results of this report show methods for maintaining out of band stability, while decreasing stability margin at specific bands. Decreasing stability can enhance the gain under controlled conditions. The large signal gain obtained at approximately 15W output power for both selected frequency bands are around 15.2dB.Detta kandidatexamensarbete omfattar grunderna i hur en stabil transistorbaserad förstärkarkrets designas. Uppgiften var att designa en ingångs match för att öka förstärkningen för en specifik transistor. Transistorn CGH60015D är utvecklad av Cree Inc. När den här transistorn stabiliseras förloras mycket av den tillgängliga förstärkningen. Det största problemet är att den inte kan levera hög förstärkning medan den är stabil. För att förbättra förstärkningen används en ingångsmatch som ska klara av två frekvens band och på sådant sätt öka gainet över dessa band. Arbetet täcker grunderna för att designa ett matchningsnätverk till en transistor, och hur man kan analysera kretsar mer ingående för att få en så realistisk simulering som möjligt. I detta projekt har ADS och modeller av GH60015D använts för att göra simuleringar av komponenter tänkta att tillverkas på ett glassubstrat. Det eftersökta resultatet av arbetet är att få ut så mycket storsignalsförstärkning som möjligt vid frekvenserna 2.11-2.17GHz och 2.62-2.69GHz. Resultatet av denna rapport visar metoder att bibehålla ovillkorligt utombandsstabilitet, medan man vid specifika band minskar stabilitetsmarginalen för att öka förstärkningen under kontrollerade villkor. Erhållen storsignalsförstärkning vid ungefär 15W uteffekt för de båda utvalda banden är ungefär 15.2 dB.
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Sam-giao, Diane. "Etude optique de nanofils GaN et de microcavités GaN/AIN." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00870498.
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Ce travail de thèse porte sur l'étude optique de nanofils de GaN et de microcavités d'AlN contenant des boîtes quantiques de GaN. La largeur de raie de l'exciton lié au donneur neutre dans le spectre de photoluminescence des nanofils de GaN crûs par épitaxie par jets moléculaires met en evidence l'homogénéité des contraintes dans le matériau. S'ils ne présentent aucun confinement excitonique, la géométrie filaire permet une relaxation efficace des contraintes et permet d'étudier précisément le bord de bande du GaN relaxé en phase cubique. Par ailleurs, nous infirmons l'attribution de la transition à 3.45 eV observée dans le spectre des nanofils de GaN wurtzite à un satellite à deux électrons. En effet, les règles de sélection de son dipôle, ainsi que son évolution sous champ magnétique intense, montrent que cette transition n'a pas les propriétés d'un satellite à deux électrons. Nous avons également étudié la spectroscopie de microdisques d'AlN contenant des boîtes quantiques de GaN. Des facteurs de qualité record pour les cavités en AlN ont été mesurés autour de 3 eV. Des nanocavités d'AlN contenues dans des guides d'onde unidimensionnels ont également été étudiées. L'attribution de chaque mode au guide d'onde ou à la cavité, prédite par des calculs préliminaires, est confirmée expérimentalement par une localisation différente. Ces structures donnent lieu à d'excellents facteurs de qualité, de 2300 à 3.45 eV, jusqu'à 4400 à 3.14 eV. Si le facteur de Purcell attendu est très élevé (autour de 100), nous n'avons pas réussi à observer l'effet Purcell. Ceci s'explique soit par l'instabilité des modes de cavité et de l'émission des boîtes quantiques sous exposition prolongée, soit par l'importance des recombinaisons non radiatives. Enfin, il apparaît que le frein principal à l'obtention de l'effet laser dans ces structures est l'important champ électrique interne, qui ralentit l'émission spontanée des boîtes quantiques.
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Sam-Giao, Diane. "Etude optique de nanofils GaN et de microcavités GaN/AIN." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENY075/document.
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Ce travail de thèse porte sur l'étude optique de nanofils de GaN et de microcavités d'AlN contenant des boîtes quantiques de GaN. La largeur de raie de l'exciton lié au donneur neutre dans le spectre de photoluminescence des nanofils de GaN crûs par épitaxie par jets moléculaires met en evidence l'homogénéité des contraintes dans le matériau. S'ils ne présentent aucun confinement excitonique, la géométrie filaire permet une relaxation efficace des contraintes et permet d'étudier précisément le bord de bande du GaN relaxé en phase cubique. Par ailleurs, nous infirmons l'attribution de la transition à 3.45 eV observée dans le spectre des nanofils de GaN wurtzite à un satellite à deux électrons. En effet, les règles de sélection de son dipôle, ainsi que son évolution sous champ magnétique intense, montrent que cette transition n'a pas les propriétés d'un satellite à deux électrons. Nous avons également étudié la spectroscopie de microdisques d'AlN contenant des boîtes quantiques de GaN. Des facteurs de qualité record pour les cavités en AlN ont été mesurés autour de 3 eV. Des nanocavités d'AlN contenues dans des guides d'onde unidimensionnels ont également été étudiées. L'attribution de chaque mode au guide d'onde ou à la cavité, prédite par des calculs préliminaires, est confirmée expérimentalement par une localisation différente. Ces structures donnent lieu à d'excellents facteurs de qualité, de 2300 à 3.45 eV, jusqu'à 4400 à 3.14 eV. Si le facteur de Purcell attendu est très élevé (autour de 100), nous n'avons pas réussi à observer l'effet Purcell. Ceci s'explique soit par l'instabilité des modes de cavité et de l'émission des boîtes quantiques sous exposition prolongée, soit par l'importance des recombinaisons non radiatives. Enfin, il apparaît que le frein principal à l'obtention de l'effet laser dans ces structures est l'important champ électrique interne, qui ralentit l'émission spontanée des boîtes quantiquesThis work focuses on the optical study of GaN nanowires and AlN microcavities containing GaN quantum dots. The 1-meV linewidth of the neutral donor-bound exciton line in the photoluminescence spectrum of MBE-grown GaN nanowires evidences that the strain is homogeneous in the material. These nanowires do not exhibit any excitonic confinement, but the efficient strain relaxation allows to grow strain-free zinc-blende GaN nanowires and then to conduct fine spectroscopy on cubic GaN near band edge. Beside, we show that the tentative attribution of the recombination line at 3.45 eV in the spectrum of wurtzite GaN nanowires to a surface-enhanced two-electron satellite does not hold. Indeed, its dipole polarization selection rules and its evolution with intense applied magnetic field do not match that of a two-electron satellite. We also performed the spectroscopy of GaN/AlN quantum dot microdisks. Record quality factors for AlN cavities were measured around 3 eV. GaN/AlN quantum dot nanocavities embedded in photonic crystal waveguides were also investigated. The attribution of each mode either to the waveguide or to the cavity, predicted by calculations, is experimentally confirmed by a different light localization. These structures allow excellent quality factors to be reached, from 2300 at 3.45 eV, up to 4400 at 3.14 eV. Although the expected Purcell factor is very high (around 100), we did not manage to observe the Purcell effect. This originates either from an enhancement of non-radiative recombination channels or from an instability of both the cavity modes and the quantum dot emission under intense exposure. Finally, it appears that the main limiting factor to achieve lasing in these structures is the strong built-in electric field, which slows up the spontaneous emission rate of the quantum dots
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Frayssinet, Eric. "Elaboration et étude d'hétérojonctions GaN/AlGaN déposées sur GaN massif." Montpellier 2, 2000. http://www.theses.fr/2000MON20064.
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Ce travail de recherche porte sur les cristaux de gan massifs et sur les heterostructures gan/algan. Dans le premier chapitre, nous exposons les principales techniques experimentales qui nous serviront a caracteriser les cristaux massifs de gan et les couches homoepitaxiees, a savoir la spectroscopie infrarouge et -raman, la photoluminescence et la double diffraction de rayons x. Dans le second chapitre, nous etudions deux types de cristaux massifs de gan : pour les cristaux non intentionnellement dopes, nous etablissons que la face polarisee (000 $$1)n possede toujours plus de porteurs libres que la face (0001)ga et mettons en evidence la presence d'un gradient de concentration en electrons libres le long de l'axe polaire c (0001). En outre, nous revelons que les defauts natifs de lacunes de gallium sont plus nombreux sur la face (0001)ga. Les cristaux dopes magnesium, a caractere semi-isolant, permettent l'etude des phonons au centre de la zone de brillouin ainsi que les processus a deux phonons. Dans le troisieme chapitre, nous etudions les couches de gan deposees par epvom sur les deux types de cristaux de gan. Nous montrons que la meilleure face des substrats de gan pour l'homoepitaxie est la face (0001)ga. En effet, les couches deposees sur cette face incorporent beaucoup moins d'impuretes donatrices (o et si) et possedent donc moins de porteurs libres que les couches deposees sur la face (000 $$1)n. Dans le dernier chapitre, nous etudions les proprietes du gaz d'electrons 2d dans les heterostructures gan/algan deposees sur gan massif par ejm. Nous obtenons la meilleure mobilite electronique a basse temperature jamais atteinte dans un systeme a base de gan. En outre, nous determinons le facteur de lande en etudiant la dependance angulaire de l'amplitude des oscillations de shubnikov de haas. Enfin, nous concluons par la presentation du premier transistor a effet de champ (hfet) developpe sur cristaux massifs de gan.
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Qiao, Dongjiang. "GaN processing technologies /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3071033.
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Wang, Ke, and 王科. "Some experimental studies of n-type GaN and Au/GaN contacts." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B26663612.
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PecharromaÌn-Gallego, RauÌl. "Investigations of the luminescence of GaN and InGaN/GaN quantum wells." Thesis, University of Strathclyde, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400328.
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Nakazawa, Satoshi. "Interface Charge Engineering in AlGaN/GaN Heterostructures for GaN Power Devices." Kyoto University, 2019. http://hdl.handle.net/2433/244553.
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Liu, Tian-Yu. "Transmission electron microscopy studies of GaN/[gamma]-LiAlO2 [GaN/gamma-LiAlO2] heterostructures." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=975832999.
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Wang, Yingjuan. "Comprehensive optical spectroscopic investigations of GaN epilayers and InGaN/GaN quantum structures." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37090343.
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Wang, Hongjiang, and 王泓江. "Spectroscopic investigation of optical properties of GaN epilayers andInGaN/GaN quantum wells." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B29779911.
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Wang, Yingjuan, and 王穎娟. "Comprehensive optical spectroscopic investigations of GaN epilayers and InGaN/GaN quantum structures." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B37090343.
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Neubert, Barbara Monika. "GalnN /GaN LEDs auf semipolaren Seitenfacetten mittels selektiver Epitaxie hergestellter GaN-Streifen." Göttingen Cuvillier, 2008. http://d-nb.info/99081145X/04.
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Faruque, Shams Omar. "Power GaN FET Testing." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1418392583.
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Foussekis, Michael. "Band Bending in GaN." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/1781.
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Steady-state and transient surface photovoltages in undoped GaN are studied in various environments (air, nitrogen, oxygen, vacuum) at room temperature and 400 K with a Kelvin probe attached to an optical cryostat. The results are explained within a phenomenological model accounting for the accumulation of photo-generated holes at the surface, capture of free electrons from the bulk over the near-surface potential barrier, and emission of electrons from surface states into the bulk. Mechanisms of surface photovoltage are discussed in detail. Photoadsorption and photodesorption of negatively charged species will either increase or decrease the surface potential and thus band bending. Oxygen is the assumed species responsible for the SPV changes in air ambient during continuous UV illumination. This variation in SPV will be confirmed with photoluminescence measurements.
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Fikry, Mohamed [Verfasser]. "Epitaxial growth and characterization of coaxial GaN/InGaN/GaN nano-structures / Mohamed Fikry." Ulm : Universität Ulm. Fakultät für Ingenieurwissenschaften und Informatik, 2015. http://d-nb.info/1067924337/34.
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Hestroffer, Karine. "Croissance et caractérisation de nanofils de GaN et d'hétérostructures filaires de GaN/AIN." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00863433.
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Ce travail de thèse porte sur la croissance par épitaxie par jets moléculaires assistée plasma et sur la caractérisation de nanofils (NF) de GaN et d'hétérostructures filaires de GaN/AlN. Dans un premier temps, la morphologie des NFs de GaN (densité, longueur moyenne, diamètre moyen, dispersion de longueurs) est étudiée en fonction des paramètres de croissance. Via la diffraction d'électrons rapides, la morphologie des NFs GaN est corrélée à la dynamique de nucléation de ces derniers. Des expériences de diffraction de rayons X en incidence rasante effectuées à l'ESRF permettent également de clarifier les processus de nucléation des NFs GaN. Nous démontrons ensuite l'utilisation de la diffraction de rayons X résonnante pour déterminer la polarité des NFs GaN. Nous montrons que ces derniers sont de polarité N lorsque fabriqués sur Si nu. Des tests complémentaires de gravure sélective au KOH révèlent que les NFs GaN fabriqués sur un substrat de Si recouvert d'un fin buffer d'AlN ainsi que ceux dont la fabrication est initiée après pré-déposition de Ga sur la surface du Si, sont aussi de polarité N. Concernant les hétérostructures filaires GaN-AlN, la croissance d'AlN autour et sur les nanofils de GaN est étudiée en fonction de divers paramètres de croissance. Le rapport d'aspect des coquilles d'AlN (longueur/épaisseur) est décrit par un modèle géométrique. En utilisant une combinaison de diffraction anomale multi-longueurs d'onde, de microscopie en transmission de haute résolution et des calculs théoriques, l'état de contrainte des coeurs de GaN est analysé en fonction de l'épaisseur de la coquille. Cette contrainte augmente avec l'épaisseur de la coquille tant que l'AlN croît de manière homogène autour des NFs de GaN. Dès lors que la coquille est asymétrique, le système relaxe plastiquement. Nous étudions enfin la possibilité de fabriquer des îlots de GaN dans des NFs AlN. Nous déterminons le rayon critique de NFs AlN au-dessus duquel le GaN déposé subit une transition de forme de 2D à 3D. L'analyse des propriétés optiques de ces nanostructures originales revèle la présence de nombreux états localisés.
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SIOZADE, LAURE. "Spectroscopie optique de couches massives de gan et d'heterostructures (in,ga)n/gan." Clermont-Ferrand 2, 2000. http://www.theses.fr/2000CLF22254.
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Ce memoire a trait a l'analyse experimentale et theorique des proprietes optiques et electroniques de materiaux semi-conducteurs nitrures a base d'elements iii. Les proprietes optiques de couches massives de gan epitaxiees sur substrat saphir ont ete etudiees. La spectroscopie de reflectivite associee a une modelisation des polaritons dans une approche non locale a permis d'analyser les effets de la contrainte et de la temperature sur les structures excitoniques de gan : calibration de l'etat de contrainte residuelle des couches, determination des parametres d'interaction exciton-phonon et des forces d'oscillateurs. L'utilisation combinee d'experiences de reflectivite et d'ellipsometrie a conduit a la determination de la variation de l'indice optique de gan en fonction de la longueur d'onde entre 4 k et 300 k. L'etude des proprietes d'absorption et d'emission d'heterostructures (in, ga)n/gan elaborees par epitaxie par jets moleculaires sur une structure gan massif/ saphir a pu etre menee grace a l'utilisation de deux techniques spectroscopiques : l'absorption optique detectee thermiquement (aodt) et la photoluminescence (pl). Tous les spectres experimentaux etant structures par des oscillations attribuees aux interferences dans la couche massive de gan, une procedure a ete developpee afin d'eliminer ces oscillations sur les spectres de pl en vue d'ameliorer l'analyse spectroscopique. Un modele d'absorption a egalement ete elabore en vue d'ajuster les spectres d'aodt et de determiner les coefficients d'absorption ainsi que les energies de transitions. Le parametre de courbure relatif a l'energie de bande interdite de l'alliage contraint a donc pu etre deduit. La confrontation des resultats d'aodt et de pl obtenus sur des structures bidimensionnelles d'epaisseurs variables a permis de confirmer et mesurer un decalage de stokes important dont l'origine est attribuee a l'effet d'un champ interne important et/ou au processus de localisation des porteurs.
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Wu, Mo. "AlGaN/GaN Dual Channel HFETs and Realization of GaN Devices on different substrates." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/403.
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GaN-based HFETs demonstrate ubiquitous high power and high frequency performance and attract tremendous research efforts. Even though significant advances have been achieved, there still exist some critical issues needed to be investigated and solved. In particular, high defect densities due to inhomogeneous growth and operation under high power conditions bring many unique problems which are not so critical in the conventional Si and GaAs materials systems. In order to reduce the defect density and heat dissipation of GaN-based HFETs, research work on the realization of GaN-based HFETs on bulk GaN substrate has been carried out and the key problems have been identified and solved. Hot phonon scattering is the bottleneck which limits the enhancement of electron velocity in the GaN 2DEG channel. It is found that the plasmon-phonon coupling is the mechanism for converting of hot phonons into high group velocity acoustic phonons. In order to push more electrons into the GaN 2DEG channel in the plasmon-phonon coupling regime and to further reduce the hot phonon lifetime, a novel AlGaN/GaN dual channel HFET structure has been proposed. The growth, fabrication and characterization of such a AlGaN/GaN dual channel HFET structure has been carried out. Conventionally GaN-based light emitting diodes and laser diodes are grown and fabricated using the c-plane III-nitride expitaxy layers. In c-plane III-nitride epi-layers, the polarization-induced electric field introduces spatial separation of electron and hole wave functions in quantum wells (QW)s used LEDs and laser diodes LDs and degrades quantum efficiency. As well, blueshift in the emission wavelength becomes inevitable with increasing injection current unless very thin QWs are employed. The use of nonpolar orientations, namely, m-plane or a-plane GaN, would solve this problem. So far, m-plane GaN has been obtained on LiAlO2 (100), m-plane SiC substrates, and m-plane bulk GaN, which all have limited availability and/or high cost. Silicon substrates are very attractive for the growth of GaN due to their high quality, good thermal conductivity, low cost, availability in large size, and ease with which they can be selectively removed before packaging for better light extraction and heat transfer when needed To realize the low cost and improve the internal quantum efficiency of GaN based light emitting diodes, the process for m-plane GaN growth on Si (112) substrates has been studied and optimized. The continuous m-plane GaN film is successfully grown on Si (112) substrates.
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Ive, Tommy. "Growth and investigation of AlN/GaN and (Al,In)N/GaN based Bragg reflectors." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=978915607.
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Behmenburg, Hannes [Verfasser]. "Comprehensive study on MOVPE of InAlN/GaN HEMT structures and GaN nanowires / Hannes Behmenburg." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2013. http://d-nb.info/1036302067/34.
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Mehlhose, Sven [Verfasser], and Motomu [Akademischer Betreuer] Tanaka. "Biofunctionalization of GaN/AlGaN/GaN High Electron Mobility Transistors / Sven Mehlhose ; Betreuer: Motomu Tanaka." Heidelberg : Universitätsbibliothek Heidelberg, 2019. http://d-nb.info/1188110861/34.
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Ive, Tommy. "Growth and investigation of AlN/GaN and (Al,In)N/GaN based Bragg reflectors." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2006. http://dx.doi.org/10.18452/15395.
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Die Synthese von AlN/GaN- und (Al,In)N/GaN-Braggreflektoren wird untersucht. Die Strukturen wurden mittels plasmaunterstützter Molekularstrahlepitaxie auf 6H-SiC(0001)-Substraten abgeschieden. Ferner wurde der Einfluß der Si-Dotierung auf die Oberflächenmorphologie sowie die strukturellen und elektrischen Eigenschaften der AlN/GaN-Braggreflektoren untersucht. Es wurden rißfreie Braggreflektoren mit einer hohen Reflektivität (R>99%) und einem bei 450 nm zentrierten Stopband erhalten. Die Si-dotierten Strukturen weisen eine ohmsche I-V-Charakteristik im gesamten Meßbereich sowie einen spezifischen Widerstand von 2-4 mOhmcm2 auf. Die Ergebnisse der (Al,In)N-Wachstumsversuche wurden in einem Phasendiagramm zusammengefaßt, welches den optimalen Parameterraum für (Al,In)N klar aufzeigt.We study the synthesis of AlN/GaN and (Al,In)N/GaN Bragg reflectors. The structures were grown by plasma-assisted molecular beam epitaxy (MBE) on 6H-SiC(0001) substrates. In addition, we study the impact of Si-doping on the surface morphology and the structural and electrical properties of the AlN/GaN Bragg reflectors. Crack-free and high-reflectance (R>99%) Bragg reflectors were achieved with a stopband centered at 450 nm. The Si-doped structures exhibit ohmic I-V behavior in the entire measurement range. The specific series resistance is 2-4 mOhmcm2. The results of the (Al,In)N growth experiments are summarized in a phase diagram which clearly shows the optimum growth window for (Al,In)N.
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Ehteshamuddin, Mohammed. "Design of a High Temperature GaN-Based Variable Gain Amplifier for Downhole Communications." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/74958.
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The decline of easily accessible reserves pushes the oil and gas industry to explore deeper wells, where the ambient temperature often exceeds 210 °C. The need for high temperature operation, combined with the need for real-time data logging has created a growing demand for robust, high temperature RF electronics. This thesis presents the design of an intermediate frequency (IF) variable gain amplifier (VGA) for downhole communications, which can operate up to an ambient temperature of 230 °C. The proposed VGA is designed using 0.25 μm GaN on SiC high electron mobility transistor (HEMT) technology. Measured results at 230 °C show that the VGA has a peak gain of 27dB at center frequency of 97.5 MHz, and a gain control range of 29.4 dB. At maximum gain, the input P1dB is -11.57 dBm at 230 °C (-3.63 dBm at 25 °C). Input return loss is below 19 dB, and output return loss is below 12 dB across the entire gain control range from 25 °C to 230 °C. The variation with temperature (25 °C to 230 °C) is 1 dB for maximum gain, and 4.7 dB for gain control range. The total power dissipation is 176 mW for maximum gain at 230 °C.Master of Science
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Khalil, Ibrahim. "Intermodulation distortion in GaN HEMT." Göttingen Cuvillier, 2009. http://d-nb.info/1000063275/04.
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Taking, Sanna. "AlN/GaN MOS-HEMTs technology." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3356/.
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The ever increasing demand for higher power devices at higher frequencies has prompted much research recently into the aluminium nitride/gallium nitride high electron mobility transistors (AlN/GaN HEMTs) in response to theoretical predictions of higher performance devices. Despite having superior material properties such as higher two-dimensional electron gas (2DEG) densities and larger breakdown field as compared to the conventional aluminium gallium nitride (AlGaN)/GaN HEMTs, the AlN/GaN devices suffer from surface sensitivity, high leakage currents and high Ohmic contact resistances. Having very thin AlN barrier layer of ∼ 3 nm makes the epilayers very sensitive to liquids coming in contact with the surface. Exposure to any chemical solutions during device processing degrades the surface properties, resulting in poor device performance. To overcome the problems, a protective layer is employed during fabrication of AlN/GaN-based devices. However, in the presence of the protective/passivation layers, formation of low Ohmic resistance source and drain contact becomes even more difficult. In this work, thermally grown aluminium oxide (Al2O3) was used as a gate di- electric and surface passivation for AlN/GaN metal-oxide-semiconductor (MOS)-HEMTs. Most importantly, the Al2O3 acts as a protection layer during device processing. The developed technique allows for a simple and effective wet etching optimisation using 16H3PO4:HNO3:2H2O solution to remove Al from the Ohmic contact regions prior to the formation of Al2O3 and Ohmic metallisation. Low Ohmic contact resistance (0.76Ω.mm) as well as low sheet resistance (318Ω/square) were obtained after optimisation. Significant reduction in the gate leakage currents was observed when employing an additional layer of thermally grown Al2O3 on the mesa sidewalls, particularly in the region where the gate metallisation overlaps with the exposed channel edge. A high peak current ∼1.5 A/mm at VGS=+3 V and a current-gain cutoff frequency, fT , and maximum oscillation frequency, fMAX , of 50 GHz and 40 GHz, respectively, were obtained for a device with 0.2 μm gate length and 100 μm gate width. The measured breakdown voltage, VBR, of a two-finger MOS-HEMT with 0.5μm gate length and 100 μm gate width was 58 V. Additionally, an approach based on an accurate estimate of all the small-signal equivalent circuit elements followed by optimisation of these to get the actual element values was also developed for AlN/GaN MOS-HEMTs. The extracted element values provide feedback for further device process optimisation. The achieved results indicate the suitability of thermally grown Al2O3 for AlN/GaN-based MOS-HEMT technology for future high frequency power applications.
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Li, Tian. "Growth and characterisation of GaN." Thesis, Nottingham Trent University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272801.
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Morris, Robin David. "NMR of zinc-blende GaN." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438411.
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Jiang, Sheng. "All-GaN integrated cascode configuration." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/20183/.
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Zhang, Yuhao Ph D. Massachusetts Institute of Technology. "GaN-based vertical power devices." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112002.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 163-170).
Power electronics based on Gallium Nitride (GaN) is expected to significantly reduce the losses in power conversion circuits and increase the power density. This makes GaN devices very exciting candidates for next-generation power electronics, for the applications in electric vehicles, data centers, high-power and high-frequency communications. Currently, both lateral and vertical structures are considered for GaN power devices. In particular, vertical GaN power devices have attracted significant attention recently, due to the potential for achieving high breakdown voltage and current levels without enlarging the chip size. In addition, these vertical devices show superior thermal performance than their lateral counterparts. This PhD thesis addresses several key obstacles in developing vertical GaN power devices. The commercialization of vertical GaN power devices has been hindered by the high cost of bulk GaN. The first project in this PhD thesis demonstrated the feasibility of making vertical devices on a low-cost silicon (Si) substrate for the first time. The demonstrated high performance shows the great potential of low-cost vertical GaN-on-Si devices for 600-V level high-current and high-power applications. This thesis has also studied the origin of the off-state leakage current in vertical GaN pn diodes on Si, sapphire and GaN substrates, by experiments, analytical calculations and TCAD simulations. Variable-range-hopping through threading dislocations was identified as the main off-state leakage mechanism in these devices. The design space of leakage current of vertical GaN devices has been subsequently derived. Thirdly, a novel GaN vertical Schottky rectifier with trench MIS structures and trench field rings was demonstrated. The new structure greatly enhanced the reverse blocking characteristics while maintaining a Schottky-like good forward conduction. This new device shows great potential for using advanced vertical Schottky rectifiers for high-power and high-frequency applications. Finally, we investigated a fundamental and significant challenge for GaN power devices: the lack of reliable and generally useable patterned pn junctions. Two approaches have been proposed to make lateral patterned pn junctions. Two devices, junction barrier Schottky devices and super-junction devices, have been designed and optimized. Preliminary experimental results were also demonstrated for the feasibility of making patterned pn junctions and fabricating novel power devices.
by Yuhao Zhang.
Ph. D.
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Alexis, Jean-Paul. "Croissance de GaN par MOVPE." Montpellier 2, 1997. http://www.theses.fr/1997MON20108.
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Gan est un materiau semiconducteur tres prometteur, tant pour l'optoelectronique, que pour les transistors hyperfrequence, de puissance et les photodetecteurs ultraviolets. Le principal probleme a resoudre est la croissance du materiau, du fait qu'il n'existe pas de substrat adapte. La technique de croissance la plus performante pour ce materiau a l'heure actuelle est la movpe, en utilisant une couche tampon qui permet de resoudre le probleme d'accord de maille avec le substrat (generalement du saphir). Dans ce travail, nous avons etudie et optimise le procede de depot de gan par movpe sur une couche tampon de gan deposee a basse temperature. Du materiau de tres haute qualite a ainsi pu etre fabrique, apres une optimisation systematique des parametres de croissance.
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Jogi, Sreeram. "Modelling of GaN Power Switches." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1431717800.
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Alrrshedan, Marrwa. "Photoluminescence from Bulk GaN Substrates." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2802.
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Photoluminescence (PL) has been studied from different types of bulk GaN samples grown by hydride vapor phase epitaxy technique at Kyma Technologies. Point defects in bulk and at the surface affect the electrical and optical properties of GaN and could be analyzed by PL. The surface of the samples was polished with different techniques: one is chemical mechanical polish (CMP) and another is mechanical polish (MP). PL data from MP and CMP surfaces show that PL intensity from the CMP-treated surface is much higher than that from the MP-treated surface. This can be explained by defects formed during the process of MP polish. However, after the MP-treated surface is etched with RIE method, the optical quality of the MP-treated surface improves. In particular, as the depth of etching increases from 50 nm to 700 nm, the PL intensity increases by a factor of 1000. PL from the CMP surfaces of undoped bulk GaN samples contains a broad red luminescence (RL) band and a broad green luminescence (GL) band. However, PL from the CMP surfaces of Fe-doped GaN samples contained a blue luminescence band (labeled as BL2 in literature) and the yellow luminescence (YL) band. PL from MP-treated surfaces (both undoped and Fe-doped) was very weak and it contained relatively narrow red and green bands. These bands, labeled RL2 and GL2, respectively, are quenched at relatively low temperatures, in contrast to the RL and GL bands which are almost independent of temperature in the range from 15 to 300 K.
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Niu, Nan. "GaN/InGaN Microcavities and Applications." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:17467361.
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Semiconductor micro- and nano-cavities are excellent platforms for experimental studies of optical cavities, lasing dynamics, and cavity Quantum Electrodynamics (QED). Common materials for such experiments are narrow bandgap semiconductor materials with well-developed epitaxial growth technologies, such as GaAs and InP, among others. Gallium nitride (GaN) and its alloys are industrially viable materials with wide direct bandgaps, low surface re-combination velocities, and large exciton binding energies, offering the possibility of room temperature realization of light-matter interaction. Controlling light-matter interaction is at the heart of nanophotonic research which leads to ultra-low threshold lasing, photonic qubits, and optical strong coupling. Technologically, due to its blue emission, GaN photonic cavities with indium gallium nitride (InGaN) active mediums serve as efficient light sources for the fast growing photonic industry, optical computing and communication networks, display technology, as well as quantum information processing.
The main challenges in fabricating high quality GaN cavity are due to its chemical inertness and low material quality as a result of strain-induced defects and threading dislocations. In this dissertation, I examine the designs, novel fabrication processes, and characterizations of high quality factor GaN microdisk and photonic crystal nanobeam cavities with different classes of InGaN active medium, namely quantum dots (QDs), quantum wells (QWs), and fragmented quantum wells (fQWs), for investigating light-matter interaction between cavity and these active media.
This dissertation is carefully organized into four chapters. Chapter 1 outlines the background of the research, the materials and growth, and the necessary technique Photoelectrochemical (PEC) etching which is uniquely used to undercut and suspend GaN cavities.
Chapter 2 outlines the fabrications, optical experiments, and tuning technique developed for GaN/InGaN microdisks. Microdisks are circular resonant cavities that support whispering gallery modes. Through the use of optimized dry etching and PEC, high quality factor microdisks with relatively small modal volume are fabricated with immediate demonstration of low threshold lasing. On the path to achieving light and matter interactions, irreversible tuning of the cavity mode of p-i-n doped GaN/InGaN microdisks is achieved through photo-excitation in a water environment. Such a technique paves the way for deterministically and spectrally matching the cavity mode to the emitter’s principle emission.
Chapter 3 outlines the work done on the high quality GaN photonic crystal nanobeams with InGaN QDs and fQWs. The fragmented nature of the fQW layer has a surprisingly dramatic influence on the lasing threshold. A record low threshold is demonstrated that is an order of magnitude lower in threshold than identical nanobeams with homogeneous QW, and comparable to the best devices in other III-V material systems. As an active medium with greater carrier confinement than quantum wells, and higher carrier capture probability than quantum dots, the fQW active medium, in combination with the nanobeam cavity with ultra-small modal volume and high quality factor, provides an ideal means of probing the limits of light and matter interactions in the nanoscale. Moreover, GaN/InGaN nanopillars are fabricated to isolate a single InGaN QD for understanding its emission properties. Antibunching is observed, demonstrating the quantum nature of the QD emission. Gas tuning is attempted on GaN nanobeams with InGaN QDs to achieve QD-cavity mode coupling and to demonstrate cavity enhanced single photon emission. Last but not least, Chapter 4 concludes the dissertation with summary and future directions.Engineering and Applied Sciences - Applied Physics
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V, Anil Kumar T., and Anil Kumar T. V. "Nano Imprint Lithography and GaN GAA Nanowire." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/xqm526.
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碩士亞洲大學
資訊工程學系
102
Nanoimprint Lithography: Si master molds are generally patterned by electron-beam lithography (EBL) that is known to be a time consuming nano patterning technique. Thus, developing mold duplication process based on high throughput technique such as nanoimprint lithography can be helpful in reducing its fabrication time and cost. This study aims to develop capabilities in patterning nano structure using thermal nano-imprint lithography. The NEB22 A2, mr- I7000E series negative e-beam resist possess a variety of characteristics desirable for NIL, such as low viscosity, low bulk-volumetric shrinkage, high Young's modulus, high thermal stability, and excellent dry-etch resistance. The excellent oxygen-etch resistance of the barrier material enables a final transfer pattern that is about three times higher than that of the original NIL mold. Based on these imprint on negative photo resist approach is used for pattern transfer into silicon substrates. The result is a high-resolution pattern with feature sizes in the range of nanometer to several microns. We combine Simprint Core simulation software for simulating nanoimprint process and to achieve uniform RLT. Our research results in low RLT as 10-20nm thicknesses for mr-I 7020E photoresist. The simulation results and experimental results are matching. A plot of how RLT across the whole stamp region changes with imprinting duration is shown using simulation. The central, thick line shows the average RLT across the entire stamp; the thin lines indicate the stamp-average RLT plus and minus one standard deviation of the cross-stamp RLT values. Simulated and calibrated for uniform residual layer thickness (RLT) and the cross-sections of RLT are plotted. In cavity filling value of 0 denotes completely empty cavities; a value of 1 in a particular location means that cavities are completely filled in that region. We have achieved completely filled cavities, i.e., value of 1 at all locations. We have achieved RLT around 10nm and even RLT at all location in pattern using mr-I 7020E photoresist imprint. GaN GAA Nanowire: To increase typically low output drive currents from Si Nanowire field-effect transistors (FETs), we show a GaN based GAA Nanowire FET’s effectiveness. The theoretical study is focused on the three dimensional device designs, comparisons, random dopant fluctuation using IFM, and general variability issues including nanowire length, gate work function, and channel thickness are discussed. Performance of GaN GAA Nanowire is found to be increasing as Gate length is increased. Electrical characteristics of FETs including threshold voltage saturation, On/Off current ratio and sub threshold slope (SS) are analysed. GaN GAA structure let to gate control ability improvement compared to Si based Nanowire in electrical performance. The GaN GAA Nanowire subthreshold slope is ~62mV/decade, which is close to the theoretical limit 60 mV/decade and leads to very high Ion/Ioff ratio of 1010-1011. The GaN GAA Nanowire is a very promising candidate for high-performance.
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Chiu, Fang-Yuan, and 邱芳源. "Theoretical analysis of GaN resonant periodic gain lasers." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/30952582810756388597.
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碩士國立海洋大學
電機工程學系
88
Recently the wide band-gap semiconductor lasers including GaN, AlGaN, and InGaN have drawn intensive interest. These semiconductor materials can be fabricated into blue-green lasers and are useful for many optoelectronic devices applications. In this thesis, we calculate the threshold optical gain, threshold carrier concentration and output power of the optically pumped GaN-AlGaN resonant periodic gain surface-emitting semiconductor lasers. The active region of the resonant periodic gain surface-emitting semiconductor lasers consists of a series of quantum wells spaced at one half the wavelength of a particular optical transition in the quantum wells. This spatial periodicity allows the antinodes of the standing wave optical field to coincide with the gain mediums, enhances the frequency selectivity, increases the gain in the vertical direction by a factor of two, to be compared with a uniform medium or a non-resonant multiple quantum wells, and reduces amplified spontaneous emission.
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Peng, Li Yi, and 彭立儀. "Investigation of InAlN/GaN and P-GaN/AlGaN/GaN hetero-structure fields effect transistors." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/nqha6z.
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"Analysis of Heat Dissipation in AlGaN/GaN HEMT with GaN Micropits at GaN-SiC Interface." Master's thesis, 2016. http://hdl.handle.net/2286/R.I.41224.
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abstract: Gallium Nitride (GaN) based microelectronics technology is a fast growing and most exciting semiconductor technology in the fields of high power and high frequency electronics. Excellent electrical properties of GaN such as high carrier concentration and high carrier motility makes GaN based high electron mobility transistors (HEMTs) a preferred choice for RF applications. However, a very high temperature in the active region of the GaN HEMT leads to a significant degradation of the device performance by effecting carrier mobility and concentration. Thus, thermal management in GaN HEMT in an effective manner is key to this technology to reach its full potential.
In this thesis, an electro-thermal model of an AlGaN/GaN HEMT on a SiC substrate is simulated using Silvaco (Atlas) TCAD tools. Output characteristics, current density and heat flow at the GaN-SiC interface are key areas of analysis in this work. The electrical characteristics show a sharp drop in drain currents for higher drain voltages. Temperature profile across the device is observed. At the interface of GaN-SiC, there is a sharp drop in temperature indicating a thermal resistance at this interface. Adding to the existing heat in the device, this difference heat is reflected back into the device, further increasing the temperatures in the active region. Structural changes such as GaN micropits, were introduced at the GaN-SiC interface along the length of the device, to make the heat flow smooth rather than discontinuous. With changing dimensions of these micropits, various combinations were tried to reduce the temperature and enhance the device performance. These GaN micropits gave effective results by reducing heat in active region, by spreading out the heat on to the sides of the device rather than just concentrating right below the hot spot. It also helped by allowing a smooth flow of heat at the GaN-SiC interface. There was an increased peak current density in the active region of the device contributing to improved electrical characteristics. In the end, importance of thermal management in these high temperature devices is discussed along with future prospects and a conclusion of this thesis.Dissertation/Thesis
Masters Thesis Electrical Engineering 2016
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Wang, Yao-Kuo, and 王耀國. "Investigation of GaN material process--Ohmic contact on p-GaN and Eximer laser etching of GaN." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/46621230251878811346.
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碩士國立交通大學
光電工程所
88
We study the process of GaN material including ohmic contact on p-GaN and Eximer laser etching of GaN. In ohmic contact, alloy consisted of Ni/Pd/Au film deposited on p-type GaN followed by heat treatment in oxygen condition. A good ohmic characteristic and specific contact resistance as low as 1.1 ×10-4Ω-cm2 was obtained at 550℃,5min. Another approach to achieving low-resistance ohmic contact is carrier concentration improvement of p-GaN by Be-implanted . A minimum ρc =4.5×10-4Ω-cm2 and perfect ohmic was obtained by Ni/Pd/Au contact without any heat treatment. In Eximer laser processing, both pulse energy and numbers of pulse of KrF laser were varied to etch the GaN film. By changing the pulsed energy at constant pulse energy, ablation of GaN surface was observed at threshold fluence of 0.3 J/cm2. A high etching rate of 82 nm/sec was obtained at fixed laser fluence of 0.3 J/cm2. Finally, we successfully separate GaN from GaN/sapphire structures using a KrF laser pulse of 1.0 J/cm2.
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Yan, Chang Jun, and 張鈞硯. "GaN Photodetector Fabrication." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/94821981801865622822.
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碩士國防大學理工學院
電子工程碩士班
101
The Characteristics of the metal-semiconductor-metal (MSM) photodetector with different epitaxial structure were mainly discussed in this paper. One is gradual-buffer MSM structure, the other is MSM with step buffer structure. Both two samples’ P/D ratio and responsibility were compard, and MSM with and without capping layer in step structure were also analyzed. For step buffer structure of fine epitaxial quality, a band discontinuity with obvious barrier height can lower dark current and promoted photocurrent/dark ratio. A Filter layer of Mg0.44Zn0.56O deposited on electrode applied to a wavelength-selection photodetector. It’s a thin film with high resistance and wide band gap of about 4.4eV which cut-off wavelength was suitable for specific designed absorption wavelength. For thin film materials of Mg0.44Zn0.56O analysis, the transmittance of thin film was measured after high temperature annealing and XRD analysis found that Bragg’s angle changed from 34.42 ° right shift to 35.3 °. Composition of thin films was also examined by EDS . For conventional photodetector, Mg0.44Zn0.56O with the effect of passivation layer can effectively lower the dark current about three orders in magnitude, and the current contrast ratio can be achieved level of 1.27×105. Metal-semiconductor-metal structures have the original advantages of low stray capacitance, and in this paper Mg0.44Zn0.56O thin film appropriately deposited will decrease the capacitance value about one order in magnitude. The response time was improved due to low leakage current caused by diffusion capacitance decreasing and less interface defects.
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Huang, Kun-Bin, and 黃崑賓. "Investigation of Arsenic-doped GaN thin Film on GaN/Sapphire Substrates." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/ft87s7.
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碩士崑山科技大學
電機工程研究所
91
GaNAs epilayers were grown on GaN/Sapphire substrates by low-pressure metal-organic chemical vapor deposition .Tertiarybutylarsine (TBAs) was used as the As source . first，Introduction the background of development and MOCVD and the measurement of technique for XRD、PL、AFM， To following，Using the different of grow conditions on GaN/Sapphire substrates . After，Doping a few Arsenic(As) to control the lattice constant with the result that control the different wavelength，Successed to grow of Arsenic-doped GaN，proceed to measurement of the XRD、PL、AFM .
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Yang, Chang-Yi, and 楊昌義. "Epitaxy of GaN by MOCVD and Fabrication of AlGaN/GaN MODFET." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/28840002147467817767.
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碩士國立成功大學
電機工程學系
89
In this thesis, the material growth, material characterization and device fabrication of GaN material were systematically studied. We had investigated the nitridation effect on the quality of un-doped GaN epitaxial layer. High quality GaN film with the mobility of 144 cm2/V-s and the carrier concentration of 5.7x1017 cm-3 was grown with 3 min nitridation. The role of hydrogen in un-doped GaN epitaxy grown by MOCVD was also discussed. Low background concentration un-doped GaN films grown on sapphire by MOCVD were made by reducing the hydrogen flow rate, but the mobility was diminished seriously. For the lightly Si-doped GaN, we found that the electron concentration was first decreased and then raised when the flow rate of SiH4 increased. We suggested this phenomenon was due to the oxygen contamination or the nitrogen gallium antisites NGa. In the GaN-based HEMT fabrication study, we used the AlGaN/GaN heterojunction to fabricate the AlGaN/GaN MODFET with the maximum transconductance of 50 mS/mm.
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Liu, Yen-Cheng, and 劉衍昌. "Shrinking Gate Length by Oxidization Treatment in GaN/AlGaN/GaN HEMTs." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/96697322278637720041.
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碩士國立成功大學
微電子工程研究所碩博士班
97
In this work, we preset an effective method of shrinking gate length by oxidization gate metal. The oxidization method’s advantages are fast, low cost, simple and effective increase devices performance. The gate metal process to be use metal different coefficient of oxidization by oxidization treatment, and the GaN has excellent chemical and physics stability, so it is difficult to be oxidized by the H2O2. We can oxidize the gate metal by using general H2O2 after we finish the gate metal’s process. Because the different coefficient of oxidization of Ni/Au gate meal, it is effective to shrink gate length of metal below the gate.Experiment results indicate that the oxidization process can improve devices DC and microwave characteristics: the saturation drain current density IDSS0 (305mA/mm -> 322 mA/mm), the maximum extrinsic transconductance gm,max (99 mS/mm -> 114mS/mm), the pinch-off voltage Vpinch-off (–3.2 V -> –3 V), the unity current gain cut-off frequency fT (11.1 GHz -> 14.4 GHz), the maximum oscillation frequency fmax (14.6 GHz -> 17.4 GHz), the minimum noise figure NFmin (1.902 dB -> 1.384 dB) and the power-added-efficiency (P.A.E.) (24.5 % -> 31.1 %).
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Hsiao, Yu-Shan, and 蕭羽珊. "Growth of Thick GaN Layers on GaN Nanorod Template by HVPE." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/14322606400621789852.
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碩士國立中央大學
光電科學研究所
99
In this research, we used horizontal system of home-made hydride vapor phase epitaxy (HVPE) to growth thick GaN films on 2μm un-doped GaN/ sapphire substrate. We changed the growth parameters, for example, using different carrier gas, changing V/III ratio and carrier gas flow to optimize the crystal quality. Then we used optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), and atomic force microscopy (AFM) to measure the surface morphology, the thickness of epitaxial layer, and the crystal quality. We could produce high quality thick GaN template that were lower defect density, mirror-like surface, and better thickness uniformity. Then we used thick GaN template to do GaN-based light-emitting diodes (LEDs). The crystalline quality of the epitaxial film could be improved by using thick GaN template. The light output power (LOP) of LED grown on 125μm GaN template was 136% higher than those of LED grown on 2μm GaN template at the injection current of 20mA, respectively. The saturation current of LED grown on 125μm GaN template was 670mA higher than those of LED grown on 2μm GaN template that was 400mA. These measured result was explained by thermal imager measurement in this article. Finally, in order to reduce the stress causing by heteroepitaxy, we used HVPE to successfully produce above 350μm thick GaN epitaxy on GaN nanorod template. The surface of 350μm thick GaN was mirror-like surface. Compared with EPD measurement of conventional 2μm GaN template and 350μm GaN template, the EPD was reduced from 6.52×108 cm-2 to 2.00×107 cm-2 by increasing the thickness of GaN epitaxial layer.
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Lai, Kun-Yu Alvin. "InGaN/GaN quantum wells grown on polar and nonpolar GaN substrates." 2009. http://www.lib.ncsu.edu/theses/available/etd-06012009-172916/unrestricted/etd.pdf.
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Peng, Chuan-Yun, and 彭川耘. "High Quality Thick GaN Films Grown on GaN Substrates by HVPE." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/74368232788885992694.
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碩士國立交通大學
電子物理系所
99
In this work, the major purpose is growing high quality freestanding GaN substrate. In order to grow this substrate, we have to grow thicker GaN film to reduce its dislocation density. Because growing GaN thick films on sapphire substrates are crack easily by mismatch of thermal expansion. We use freestanding GaN substrate which is separate after laser lift off (LLO), and homoepitaxy to regrowth GaN thick films. In this experiment, we mainly to solve the surface oxide layer, the surface pits, and the bowing of thick films. We use wet etch to solve the problem of surface oxide layer,lateral growth to solve the problem of surface pits. Finally we change epilayer, the difference of dislocation density, and the method of N-Face regrowth to solve the bowing and stress of GaN. In the end, we grow the GaN thick film to 8000um Successfully by our improved method, and reduced the dislocation to 6x10-6cm-2.
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Hsiao, Tsung-Chieh, and 蕭琮介. "Fabrication and Characterization of Enhancement-mode p-GaN/AlGaN/GaN HEMTs." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/78769138198386419357.
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碩士國立清華大學
電子工程研究所
102
In this thesis, enhancement-mode p-GaN/AlGaN/GaN HEMTs on a silicon substrate were fabricated. The p-type doped GaN and AlGaN/GaN barrier junction can be considered as a PN junction, so using p-type GaN as gate is able to deplete the 2DEG channel at a Vg=0V, thus yielding a normally-off device. For the on-state characteristics, the threshold voltage (Vth) and the maximum transconductance (Gm,max) for the device with 2μm Lch, 5μm Lgs and 7μm Lgd is 0.3V and 45mS/mm. And the on-resistance and on/off current ratio is 3.43mΩ‧cm^2 and 10^8 for the same device. For the reverse breakdown characteristics, we use a thick buffer layer to reduce substrate leakage current and raise the capability of vertical breakdown voltage. The highest breakdown voltage for the device with Lgd=60μm is 2760V, and the best BFOM is 604 MW/cm^2 for the device with Lgd=20μm. A drain current instability that is different from the current collapse due to surface and bulk traps is observed and explained.
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Tseng, Yu Teng, and 曾裕騰. "Investigation of Current Gain Improvement of AlGaN/GaN Heterojunction Bipolar Transistors." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/6b699g.
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博士國立清華大學
電子工程研究所
105
AlGaN/GaN single heterojunction bipolar transistors (SHBTs) without using regrown emitter junction are demonstrated. Secondary ion mass spectroscopy analysis shows that a severe co-diffusion of Al and Si exists in AlGaN/GaN heterostructures grown at 780°C by plasma-assisted molecular beam epitaxy. The altered composition and doping profiles greatly degrade the common-emitter current gain of AlGaN/GaN HBTs to ≤ 0.8. A GaN spacer layer is inserted at the emitter-base junction to alleviate this problem. In an AlGaN/GaN HBT structure inserted with a 20 nm unintentionally doped GaN spacer layer, a current gain β about 2 is achieved. The current gain is improved about 2.5 times larger than the structure without the spacer layer. The light-emitting phenomenon is also demonstrated and investigated in this article. Using high resolution X-ray photoelectron spectroscopy (XPS), the surface binding energy and composition ratio of Ga and N are determined. The XPS peak shift in dry etching processed p-type GaN represents the existence of an n-type thin layer on the surface originated from nitrogen vacancies. This extra surface layer makes the formation of a low contact resistance difficult. On the contrary, a lower contact resistance is obtained when an n-type metal contact (Ti/Ai/Ti/Au) stacks is used on the etched p-type GaN surface, which confirms that the source of surface damage is coming from surface nitrogen vacancies. In order to overcome the surface damage problem in the base region, a digital etching technique is developed. The mole fraction ratio of N/Ga measured by high resolution XPS decreases from 1 to 0.706 after the conventional base-mesa process. Applying the digital etching technique to the base surface processing, the N/Ga ratio increases from 0.706 to 0.877. Besides, the base contact resistance can be reduced about 23% than the sample treated with inductively coupled plasma etching.