Excitonic parameters of GaN studied by time-of-flight spectroscopy

TL;DR

This study refines the excitonic parameters of bulk GaN using time-of-flight spectroscopy, revealing narrow exciton-polariton resonances and quantifying oscillator strengths, advancing understanding of GaN's optical properties.

Contribution

The paper introduces a refined measurement of excitonic parameters in GaN using a novel time-of-flight spectroscopy method that accounts for elastic photon scattering effects.

Findings

Homogeneous width of exciton-polariton resonances is about 10 μeV.

Oscillator strength for A exciton-polariton is 0.0022.

Oscillator strength for B exciton-polariton is 0.0016.

Abstract

We refine excitonic parameters of bulk GaN by means of time-of-flight spectroscopy of light pulses propagating through crystals. The influence of elastic photon scattering is excluded by using the multiple reflections of the pulses from crystal boundaries. The shapes of these reflexes in the time-energy plane depict the variation of the group velocity induced by excitonic resonances. Modeling of the shapes, as well as other spectra, shows that a homogeneous width of the order of 10 \mu eV characterizes the exciton-polariton resonances within the crystal. The oscillator strength of A and B exciton-polaritons is determined as 0.0022 and 0.0016, respectively.