Phonon-mode-specific lattice dynamical coupling of carriers in semiconductors using Raman and optical spectroscopic techniques

Abstract

We demonstrate a methodology for quantitative estimation of electron-phonon coupling (EPC) for each phonon mode taking base from second-order correction in polaron-energy resulting bandgap renormalization of the semiconductor by treating EPC as perturbation. This gives coupling constant (αp) for the pth phonon mode in terms of phonon energy and renormalized bandgap due to EPC. These theoretical inferences are experimentally explored using combination of optical absorption and Raman spectroscopies for Γ phonons of temperature-varied GaN and TiO2; results reveal a systematic enhancement in αp with temperature that exhibits unique percent variation of αp for each mode. A higher percent change is observed for the mode known to exhibit greater coupling strength, thereby supporting the theoretical discussions. In this paper, we provide a simpler method to directly probe quantum level phonon-specific interactions with electrons, otherwise probed with much advanced techniques. © 2022 American Physical Society.