ECE Colloquium: Marcel Filoche

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Title: Modeling Electronic Transport in Disordered Semiconductors

Abstract: In disordered or random materials, the wave functions of quantum states can be subject to a phenomenon called “wave localization.” This localization, which consists of a concentration of the wave energy in very small sub-regions of the total domain, has been demonstrated experimentally in mechanics, acoustics and quantum physics. In nitride-based semiconductor alloys in particular, the structural disorder leads to a localization of electronic states which results in a modification of the density of states, the conduction properties, the various recombination processes as well as the light absorption efficiency.

We will present a recently developed theory that reveals an underlying and universal structure, called the localization landscape (LL) [1]. This landscape allows us to define an “effective localization potential” that predicts the localization regions, the energies of the localized modes, the density of states, as well as the long-range decay of wave functions [2]. In semiconductors in particular, accounting for localization of electronic states normally requires solving in a coupled manner the Schrödinger and the Poisson equations. We will show how the LL theory allows us to create a new computational model of disordered semiconductors which avoids this time-consuming loop, leading to a 300- to 1000-fold increase of the computation speed while accounting for quantum effects at the nanometer scale such as quantum confinement or tunnelling. This model is nowadays used in semiconductor industries to design GaN-based optoelectronic devices such as LEDs.

[1] M. Filoche & S. Mayboroda, Proc. Natl Acad. Sci. (2012). 10.1073/pnas.1120432109

[2] D. Arnold et al., Phys. Rev. Lett. (2016). 10.1103/PhysRevLett.116.056602

Bio: Marcel Filoche graduated from Ecole Polytechnique in 1985 and obtained his PhD in Physics from Université Paris-Sud Orsay in 1991. He is currently CNRS Research Director at the Institut Langevin, ESPCI, Paris. His research interests are the physics of complex and disordered geometries, with an emphasis on the theoretical foundations of wave localization, including the development of the localization landscape theory in 2012.