1,721,002 research outputs found
Reliability and dynamic properties of GaN devices
Full text linkNowadays power electronics market is increasingly having the need for high effciency power conversion systems. Due to its outstanding properties in terms of high temperature, high voltage and high frequency capability, GaN material seems to be a valid candidate to provide the solution to the market requirements. In particular, GaN High Electron Mobility Transistors (GaN HEMTs) are promising devices suitable for high voltage and high power applications. In the last years, many works about GaN power HEMTs devices have been published and this confirms the huge interest in this emerging technology. Despite the outstanding performance already demonstrated of GaN HEMTs, market is still wary of this technology due to some still open reliability issues. In particular, many works have been published regarding the reliability of such devices but only few are able to predict the lifetime of such devices working in the final real application with reasonable accuracy. Many failure modes have been investigated in laboratory direct current (DC) and pulsed conditions but only few works try
to analyze the behavior of GaN HEMTs transistors in the real application environment.
The main goal of this thesis is to investigate reliability of GaN power HEMT devices during dynamic operation in real life conditions. This thesis try to identify the most important aspects that limit reliability of GaN HEMT devices in real life conditions and try to identify the failure modes during real switching operation. Many test concepts to assess performance and reliability of GaN HEMTs working in application conditions are also reported. The thesis starts by explaining the traditional state-of-the art approach used until now to assess HEMTs reliability, then introduce novel measurement concepts that are used to test devices in real switching operation close to the operative conditions of a real power converter. First of all, a novel measurement system able to assess dynamic performance and reliability of GaN devices is presented. As a result, some novel measurements concepts and the related results are reported showing that testing GaN HEMTs in real life conditions is of fundamental importance to assess performance and reliability of such devices. At the end of the thesis a methodology capable to carry out accelerated stress test in dynamic operation conditions has been found, using an external additional capacitor in parallel with the HEMT under test. We think that the concepts introduced in this thesis enable a novel test approach that can lead to the definition of a lifetime model for GaN power HEMTs able to predict the time to failure of devices working in real life conditions
New integrative tools for interactive protein structure modeling and function prediction
Full text link
A combined three-dimensional kinetic Monte Carlo and quantum chemistry study of the CVD of Si on Si(100) surfaces
No full text
An Ab Initio Rrkm/Master Equation Investigation Of Sih4 And Geh4 Decomposition Kinetics Using A Kinetic Monte Carlo Approach
No full textChallenges of introducing quantitative elementary reactions in multiscale models of thin film deposition
No full textThe implementation of detailed surface kinetic mechanisms describing the thin film growth dynamics into models of chemical vapor deposition (CVD) reactors has been a challenge for many years. In this article we review the literature concerning the study of the dynamics of the Si(100)2×1 surface and introduce a multiscale model that captures the main features of its reactivity. The model combines the results of ab initio calculations with an atomistic description of the Si surface, obtained using a 3D-kineticMonte Carlo (KMC)model that explicitly accounts for the 2×1 surface reconstruction and the formation and diffusion of Si dimers on a hydrogenated surface. At the atomistic scale, we determined pre-exponential factors and activation energies of hydrogen desorption reactions proceeding through the 2H, 3H, and 4H mechanisms. The calculated kinetic constants were embedded in the KMC model and used to simulate literature TPD experimental data. The simulations were used to fit the activation energies of hydrogen desorption reactions, which showed that DFT calculations performed with B3LYP functionals are likely to overestimate hydrogen desorption energies by up to 9 kcalmol-1, which was confirmed by successive ab initio calculations. Two examples of the solution of the KMC model in conjunction with a reactor scale model are provided, in which the coupling was performed adopting both a hierarchic and a two-way coupling strategy.We found that in the plasma deposition of nanocrystalline silicon performed at low substrate temperatures the growth proceeds through a layer-by-layer mechanism on a surface almost completely covered by hydrogen. The application of the same model to the simulation of the thermal CVD of Si showed that at intermediate growth temperatures, when the hydrogen surface concentration is high, a new hydrogen desorption mechanism, in which Si adatoms play an important role, is active. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- …
