Phonon-assisted optical absorption in silicon from first principles

TL;DR

This paper presents a first-principles computational method to accurately calculate silicon's phonon-assisted optical absorption spectrum, aligning well with experiments and applicable to optoelectronic and photovoltaic research.

Contribution

It introduces a general first-principles approach using Wannier interpolation for phonon-assisted optical absorption, enabling accurate spectrum predictions in silicon.

Findings

Good agreement with experimental spectra near absorption onset

Accurate prediction of visible-range absorption in silicon

Method applicable to other materials and processes

Abstract

The phonon-assisted interband optical absorption spectrum of silicon is calculated at the quasiparticle level entirely from first principles. We make use of the Wannier interpolation formalism to determine the quasiparticle energies, as well as the optical transition and electron-phonon coupling matrix elements, on fine grids in the Brillouin zone. The calculated spectrum near the onset of indirect absorption is in very good agreement with experimental measurements for a range of temperatures. Moreover, our method can accurately determine the optical absorption spectrum of silicon in the visible range, an important process for optoelectronic and photovoltaic applications that cannot be addressed with simple models. The computational formalism is quite general and can be used to understand the phonon-assisted absorption processes in general.