Sujet de Doctorats 2013 - IEMN

40nm ce qui va nécessiter des épitaxies avec une épaisseur de la couche de barrière très fine afin demaximiser le rapport d’aspect du transistor. Ceci pourra avoir un effet pénalisant au niveau du courantde fuite de grille et par conséquent sur la tenue en tension du transistor. Une structure de typeMISHEMT constitue une alternative qui va être étudiée afin de mieux isoler la grille du composant.Une autre partie sera orientée vers la caractérisation des transistors et circuits fabriqués par le doctorantafin de valider la technologie mise en œuvre. Celle-ci comportera notamment la caractérisationphysique basée sur des mesures type effet Hall, C(V), Raman, SIMS… Le candidat sera égalementimpliqué dans des mesures électriques et hyperfréquences.Cette thèse est une formation en co-tutelle entre l’université de Sherbrooke (Canada) au sein du Centrede Recherche en Nanofabrication et en Nano-caractérisation (CRN²) qui est l’une des infrastructuresmajeures du réseau Nano-Québec et l’université des Sciences et Technologies de Lille1 (France) ausein du laboratoire Institut d’Électronique de Microélectronique et de Nanotechnologies (IEMN) qui estun des acteurs majeurs en France pour la technologie des dispositifs GaN. Le candidat sera amené àtravailler sur les deux sites.Abstract :State of the art shows that only few studies were realized up to now at operating frequency higher than40GHz especially on silicon substrate. The goal of this thesis subject consists to develop GaN basedHEMT field effect transistors on silicon substrate working in V and W bands for different applicationssuch as aeronautics, defense, security and telecommunications. AlGaN/GaN and more recentlyInAlN/GaN HEMTs are at present the most studied devices. The objective is the fabrication of HEMTsworking at the highest frequency and delivering the highest microwave power. In this frame,demonstrators were done by HRL on silicon substrate showing the potentialities of the proposedresearch work.In this context, our objective is the optimization of the technological process on AlGaN/GaN andInAlN/GaN using material obtained by MOCVD on silicon substrate stemming from CRHEA in theframe of collaborations. The goal consists to demonstrate a power density of 2.5W/mm in V band and1.5W/mm in W band.The candidate will work on the design and fabrication of MMIC circuits from the material up to thecharacterization. He will benefit of the complementary knowhow of two laboratories: IEMN and CRN2at Sherbrooke (Canada), this last one being involved in the circuit design. The student will be involvedin an experimental work using the technological and characterization facilities available at IEMN and at3IT (Québec). The most important part of the thesis will be the optimization of the different steps of thetransistor and circuits process. The candidate must be found by experimental research and must presentgood knowledge of component physics.The candidate will work on the optimization of the different fabrication steps (marks, isolation, ohmicand Schottky contacts, thick interconnection, BCB bridges, passive elements). Specific goal will be thefabrication of transistors with a gate length of 40nm necessitating thin barrier layer to maximize theaspect ratio of the transistor. A problem regarding the leakage current and the voltage withstanding ofthe transistor will be solved. In this frame, a MISHEMT structure can be an alternative solutionpermitting to improve the gate behavior of the transistor.Another part of the thesis will be the transistor and circuit characterizations in order to validate thetechnology. In particular, physical characterization will be performed such as Hall effect, C(V), Raman,SIMS… The candidate will be also involved in electrical and microwave measurements.23