Similarity of the 3.42 eV and near-band-edge 3.47 eV luminescence bands in GaN

TL;DR

This study reveals that the 3.42 eV and near 3.47 eV luminescence bands in GaN originate from the same intrinsic source but are affected by local polarity, strain, and growth conditions, with implications for understanding GaN's optical properties.

Contribution

It demonstrates that the two luminescence bands in GaN are intrinsically related and influenced by local polarity and strain, providing new insights into their origin.

Findings

Both bands have similar temperature and power behavior.

Two absorption edges are detected at 0.35 K in nanocolumns.

Strain-induced confinement explains narrow lines between bands.

Abstract

We demonstrate that the 3.42 eV photoluminescence (PL) band in GaN is of the same intrinsic origin as the near-edge $\sim$3.47 eV band, but arises from regions of inversed polarity characterized by different strain and growth rate. Two absorption edges are thermally detected at 0.35 K in nanocolumn structures, exhibiting both bands. Micro-PL studies have shown similar temperature/power behavior of these bands, with a competition in intensity in closely spaced spots accompanied by alterations of exciton level ordering. Strain-induced one-dimensional carrier confinement in small inversion domains likely explains the discrete narrow lines observed between the bands.