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Méthodes et analyses physico-expérimentales des mécanismes liés à la résistance dynamique dans les composants HEMT GaN de puissance

Dany Hachem 1
1 LAAS-ISGE - Équipe Intégration de Systèmes de Gestion de l'Énergie
LAAS - Laboratoire d'analyse et d'architecture des systèmes
Abstract : To control the flow of electrical energy from source to load, power electronics is one of the key elements for the management of this energy. Managing and converting electrical energy requires efficient power converters, based on switches exhibiting high switching and conduction performance, at high power and high frequency. Although silicon-based devices have dominated power electronics for a long time, the physical properties of this material limit the performance of these devices in terms of maximum operating temperature, breakdown voltage, dynamic On-state resistance and switching speed. The search for promising materials exhibiting superior performance compared to silicon is therefore contemplated. Gallium nitride (GaN) is one of the materials that, thanks to its physical properties, meet the manufacturing requirements of power converters. Furthermore, the AlGaN/GaN heterostructure high electronic mobility transistor (HEMT) is a power device that contributes to the i! nnovation in power conversion technologies. However, many reliability issues affect the electrical performance of these devices and require efforts of analysis and understanding. The contributions of this work fit precisely on this topic. The characterization of the dynamic On-state resistance of GaN HEMT transistors, which is a critical problem, is necessary to understand the dynamics of certain phenomena such as trapping. In this work, we focus on characterizing the effects of trapping induced by defects that may exist in the different layers of the structure. We propose a new general measurement methodology allowing reliable and reproducible results and showing the importance of mastering the initial conditions before each measurement. These dynamic phenomena are characterized using current measurements as a function of time, realized on TLM structures coming from different technological batches, under electrical and/or optical stimulations. Two characterization me! thods of these defects are proposed. Th! e purpose of the first method is to stress the device by a negative voltage applied to the substrate to stimulate the defects located between the 2DEG channel and the substrate, while the second one consists in illuminating the device under test with a light source whose corresponding photon energy is chosen to affect only the traps present in the materials. The effect of the illumination on the contact resistances is then studied, showing a non-negligible contribution of these resistances in the total resistance and thus highlighting, for the first time, that the degradation of the dynamic on-state resistance may be due not only to phenomena in the 2DEG channel but also to phenomena at the ohmic contacts. Then, in order to study certain trapping/de-trapping mechanisms, numerical treatments, consisting of the decomposition into a sum of exponentials, are developed to process the relaxation measurements of the current as a function of time. The variation of the relative resi! stance with a model of two resistances in series is also discussed. The results obtained confirm that the analysis of transients is a difficult problem and that the solutions to these problems are not unique. To refine these results, it will be therefore necessary to obtain the activation energies of the traps present by other methods, such as DLOS.
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Submitted on : Tuesday, July 28, 2020 - 9:47:15 AM
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Dany Hachem. Méthodes et analyses physico-expérimentales des mécanismes liés à la résistance dynamique dans les composants HEMT GaN de puissance. Micro et nanotechnologies/Microélectronique. Université Toulouse 3 Paul Sabatier (UT3 Paul Sabatier), 2020. Français. ⟨tel-02907971⟩

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