Public Thesis defense - IMCN

First-principles computation of phonon-limited carrier transport in semiconductors by Romain Claes

Pour l’obtention du grade académique de Doctorat en sciences de l’ingénieur et technologie

The electronic transport field is rapidly expanding, driven by its fundamental and practical significance in numerous modern technologies. Over the past decades, significant advancements have positioned theoretical approaches as crucial tools in the field, enabling the exploration of both established and novel systems and thus accelerating the discovery of new materials. However, it is imperative to rely on an accurate ab initio description of these properties, which are influenced by a multitude of underlying mechanisms. In this thesis, our primary focus has been on intrinsic carrier transport resulting from electron-phonon scattering. To perform high accuracy computations based on the Boltzmann transport formalism, we develop a workflow infrastructure within the Abinit software, enabling one of the pioneering high-throughput studies of carrier mobility based on first-principles. Going beyond the material screening aspect of this work, we also undertake a comprehensive review of the main approximations employed in this formalism over the last decade, highlighting how these simplifications can introduce significant errors.

In a second stage, we delves into specific systems, including the thermoelectric material Ca5In2Sb6, the transparent conductive material CuI, and the tin (II) oxides family. These investigations provide insights into the unique electronic behavior of these materials, offering potential avenues for enhancing their properties. Notably, the study of the Zintl material Ca5In2Sb6 reveals a decoupling between electronic and thermal transport, a very interesting behaviour for thermoelectric applications. In CuI, one of the earliest discovered transparent conductors, we predict a theoretical upper limit to hole mobility for different carrier concentration ranges, implying potential improvements in the experimental results. Finally, we show the potential for high hole mobilities in several ternary tin (II) oxides. We also highlight the significant role of specific vibrational modes in the scattering of carriers, thereby paving the way for new avenues in structural engineering to mitigate their impact.

Jury members :

Prof. Geoffroy Hautier (UCLouvain), supervisor
Prof. Gian-Marco Rignanese (UCLouvain), supervisor
Prof. Xavier Urbain (UCLouvain), chairperson
Prof. Samuel Poncé (UCLouvain), secretary
Prof. Yaroslav Filinchuk (UCLouvain)
Dr. Alex Ganose (Imperial College London, UK)
Prof. Alexandra Zevalkink (Michigan State University, USA)

Pay attention :

The public defense of Romain Claes scheduled for Thursday 25 January at 04:00 p.m will also take place in the form of a video conference

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