Abstract: Wide bandgap materials such as GaN and SiC as well as ultra-wide bandgap like diamond offer the potential for greatly improved power electronic device performance due to their predicted higher breakdown fields limited by avalanche breakdown, as well as their favorable transport characteristics such as high mobility and drift velocity, which reduce on-resistance and allow for high frequency operation in power conversion applications. Experimental data on the high field transport properties of such materials such as the impact ionization coefficients are relatively limited, with considerable variability. Hence, to understand the limits of performance of these materials, we have investigated the high field transport properties of wide bandgap materials using particle based full-band Cellular Monte Carlo (CMC) high field transport simulation.
 
In this talk, we will discuss material and device simulation based on the CMC method in comparison to experiment for both GaN and diamond. In particular, for diamond, we employ first principles approaches using electronic structure computed using the GW method based (BerkeleyGW code), and use this to calculate the electron-phonon scattering rates directly using the EPW (electron-phonon using Wannier) code. The impact ionization rate is derived similarly from first principles electronic structure. One important observation is that while the critical field depends strongly on the material bandgap, the relative magnitude of the deformation potential plays an important role as well, where we compare different approximations of the deformation potential in relation to the simulated impact ionization coefficients and their impact on breakdown.

Bio: Stephen M. Goodnick is currently the David and Darleen Ferry Professor of Electrical Engineering at Arizona State University. He served as Chair and Professor of Electrical Engineering with Arizona State University, Tempe, from 1996 to 2005. He served as Associate Vice President for Research for Arizona State University from 2006-2008, and presently serves as Deputy Director of ASU Lightworks as well as the DOE ULTRA Energy Frontier Research Center.  He is also a Hans Fischer Senior Fellow with the Institute for Advanced Studies at the Technical University of Munich. Professionally, he served as President (2012-2013) of the IEEE Nanotechnology Council, and served as President of IEEE Eta Kappa Nu Electrical and Computer Engineering Honor Society Board of Governors, 2011-2012. Some of his main research contributions include analysis of surface roughness at the Si/SiO2 interface, Monte Carlo simulation of ultrafast carrier relaxation in quantum confined systems, global modeling of high frequency and energy conversion devices, full-band simulation of semiconductor devices, transport in nanostructures, and fabrication and characterization of nanoscale semiconductor devices. He has published over 450 journal articles, books, book chapters, and conference proceeding, and is a Fellow of IEEE (2004) and AAAS (2022) for contributions to carrier transport fundamentals and semiconductor devices.

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