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Theoretical investigation of thermal transport in novel semiconductors with point defects

Abstract : In this thesis we couple the projected augmented wave formulation of density functional theory with the Boltzmann transport equation for phonons to study the thermal transport in semiconductors. In particular, a recently developed Green’s functions formalism is used to compute the phonon-defect scattering rates through evaluation of the T-matrix and application of the optical theorem. This methodology is explained and applied to study extrinsic dopants in boron arsenide (BAs) and p-type half-Heusler compounds (HHs).BAs is a novel material with promising electronic and thermal management applications in virtue of its high room-temperature thermal conductivity (κ), while p-type HHs have induced a large interest in the scientific community in the recent years in virtue of their promising thermoelectric applications in medium temperature range.In the case of boron arsenide we study a set of stable impurities that possess a dual nature of acceptors and donors, depending on which atom they substitute, and we assess how neutral and ionised dopants differently scatter phonons and reduce the thermal conductivity. We also extend our formulation to account for effects induced by the thermodynamics of defect formation and we evaluate howκis reduced by a mixing of charged and neutral acceptors and donors.In the case of half-Heuslers we study the role of the complete perturbation induced by substitutional defects on the lattice with respect to simpler models, and we give an explanation of the numerical results in term of pristine compound properties, namely electron and phonon projected density of states. Finally, we find a simple analytical model that fit the ab initio conductivity curves with few percent of errors.
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Submitted on : Thursday, November 25, 2021 - 8:04:52 PM
Last modification on : Friday, November 26, 2021 - 3:45:44 AM


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  • HAL Id : tel-03450187, version 1



Mauro Fava. Theoretical investigation of thermal transport in novel semiconductors with point defects. Materials Science [cond-mat.mtrl-sci]. Université Grenoble Alpes [2020-..], 2021. English. ⟨NNT : 2021GRALY024⟩. ⟨tel-03450187⟩



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