Photoluminescence Spectroscopy of Band Gap Shrinkage in GaN

TL;DR

This paper investigates how the band gap in n-type GaN shrinks with increasing electron concentration and temperature using photoluminescence spectroscopy, highlighting many-body effects and temperature dependence models.

Contribution

It provides experimental data and analysis on band-gap shrinkage in GaN, emphasizing the role of many-body effects and evaluating temperature dependence models.

Findings

Band-to-band transition energy decreases with higher electron concentration.

Temperature increase causes a red-shift in the band-edge transition.

The semi-empirical phonon-dispersion model fits the experimental data well.

Abstract

We present an experimental investigation of band-gap shrinkage in n-type GaN using photoluminescence spectroscopy, as a function of electron concentration and temperature. The observed systematic shift of the band-to-band transition energy to lower energies with increasing electron concentration has been interpreted as many-body effects due to exchange and correlation among majority and minority carriers. The band-to-band transition energy also shifts to lower energy with increasing temperature. The parameters that describe the temperature dependence red-shift of the band-edge transition energy are evaluated using different models and we find that the semi-empirical relation based on phonon-dispersion related spectral function leads to excellent fit to the experimental data.