First-principles study of the bandgap renormalization and optical property of ${\beta}$-LiGaO$_2$

TL;DR

This study uses first-principles calculations to analyze the bandgap renormalization and optical properties of the ultrawide bandgap semiconductor ${\beta}$-LiGaO$_2$, revealing significant zero-point motion effects and strong excitonic features.

Contribution

It provides a detailed first-principles analysis of electron-phonon interactions and excitonic effects in ${\beta}$-LiGaO$_2$, which were not previously characterized.

Findings

Zero-point motion correction of -0.362 eV to the bandgap

Bandgap decreases monotonically with temperature

Optical spectra show strong excitonic effects

Abstract

${\beta}$-LiGaO$_2$ with an orthorhombic wurtzite-derived structure is a candidate ultrawide direct-bandgap semiconductor. In this work, using the non-adiabatic Allen-Heine-Cardona approach, we investigate the bandgap renormalization arising from electron-phonon coupling. We find a sizable zero-point motion correction of -0.362 eV to the gap at ${\Gamma}$, which is dominated by the contributions of long-wavelength longitudinal optical phonons. The bandgap of ${\beta}$-LiGaO$_2$ decreases monotonically with increasing temperature. We investigate the optical spectra by comparing the model Bethe-Salpether equation method with the independent-particle approximation. The calculated optical spectra including electron-hole interactions exhibit strong excitonic effects, in qualitative agreement with experiment. The contributing interband transitions and the binding energy for the excitonic states are analyzed.