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Home > Thèses et HDR > Thèses en 2023

26/01/2023 - Maroun ALAM

by Laurent Krähenbühl, Leleve - published on


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Maroun Alam defends his PhD on Jan. 26, 2023 at 10:00AM.
Place : INSA Lyon - Les Humanités Amphi Ouest, Villeurbanne

Analysis and characterization of the electrical performance of Gallium Nitride components

Jury :
Rapporteurs : BATUT, Nathalie ; KHATIR, Zoubir
Examinateurs : MORANCHO, Frédéric; MOREL, Abdelkrim (SuperGrid Institute)
Encadrement Ampère : PLANSON, Dominique (Directeur de thèse); MOREL Hervé (co-encadrant); PHUNG Luong-Viet (co-encadrant)

Abstract :
Silicon is nowadays the most used material in the fabrication of transistors and power diodes because it has good electrical properties and a low manufacturing cost. Whereas, for the high powers required in power electronics applications, silicon presents its limit in this field. Thus, the research oriented towards wide bandgap materials, such as silicon carbide SiC, gallium nitride GaN, and diamond is increasing. These materials are used in this field because they exhibit better electrical and physical properties such as high saturation velocity, thermal conductivity, and large critical electric field. HEMT (High Electron Mobility Transistor) transistors are built based on a heterojunction of Gallium Nitride and Aluminum-Gallium Nitride (AlGaN/GaN). The junction of these two materials creates mechanic stresses and leads to an appearance of electrons by forming a 2D gas between the two materials where there is a high density of electrons with high speeds. However, these components are not yet completely reliable even if this is being improved. Thus, the aim of this thesis is to improve the performance of power diodes based on AlGaN/GaN heterojunction, extracted from a structure of a HEMT, based on simulations by finite elements (Technology Computer-Aided Design, TCAD) and electrical and physical characterizations on these components. This work is a part of the European IPCEI/Nano 2022 project with STMicroelectronics, which aims to improve the performance of power components.
The first aim of this work is the TCAD simulations of three AlGaN/GaN heterojunction structures (HEMT Normally On, Normally-OFF and diode). To better understand the influence of the trapping phenomenon on the electrical and physical behavior of the different devices, traps were added in different regions and interfaces of the structure by varying the concentration of the traps and the activation energy. The second aim concerns electrical characterizations. Electrical characterizations were applied on 650 V Schottky diodes with an AlGaN/GaN heterojunction, and different types of stress were applied to study the evolution of the dynamic resistance. Firstly, the quasi-static stresses correspond to a transition from the off state to the on the state for a high reverse voltage. Secondly, hard switchings have been applied with a new switching bench which is the “Double Source Test”. This was used as dynamic stress. Finally, a robustness test was carried out on these diodes that aims to apply current overloads to observe the evolution of the physical parameters of the diodes after stress.

Keywords :
Transistors and power diodes, power electronics, bandgap materials, HEMT transistors, 2D gas, TCAD simulations, quasi-static stresses, hard switching