First-principles theory of nonradiative carrier capture via multiphonon emission

TL;DR

This paper introduces a first-principles methodology for calculating nonradiative carrier capture rates at defects in semiconductors, emphasizing multiphonon emission and improved electronic structure descriptions.

Contribution

It presents a novel approach combining hybrid density functional theory with supercell calculations to accurately model defect-related carrier capture processes.

Findings

Calculated hole capture coefficients agree with experiments

Insights into defect physics in wide-band-gap semiconductors

Enhanced understanding of electron-phonon interactions

Abstract

We develop a practical first-principles methodology to determine nonradiative carrier capture coefficients at defects in semiconductors. We consider transitions that occur via multiphonon emission. Parameters in the theory, including electron-phonon coupling matrix elements, are computed consistently using state-of-the-art electronic structure techniques based on hybrid density functional theory. These provide a significantly improved description of bulk band structures, as well as defect geometries and wavefunctions. In order to properly describe carrier capture processes at charged centers, we put forward an approach to treat the effect of long-range Coulomb interactions on scattering states in the framework of supercell calculations. We also discuss the choice of initial conditions for a perturbative treatment of carrier capture. As a benchmark, we apply our theory to several hole-capturing centers in GaN and ZnO, materials of high technological importance in which the role of defects is being actively investigated. Calculated hole capture coefficients are in good agreement with experimental data. We discuss the insights gained into the physics of defects in wide-band-gap semiconductors, such as the strength of electron-phonon coupling and the role of different phonon modes.