Temperature-dependent photoluminescence characteristics of GeSn epitaxial layers

TL;DR

This study investigates how temperature affects photoluminescence in GeSn epitaxial layers, revealing the role of dislocations and strain relaxation in light emission efficiency on silicon substrates.

Contribution

It introduces a novel explanation for temperature-dependent PL in GeSn layers, emphasizing the optical activity of dislocations and their impact on recombination dynamics.

Findings

Dislocation nucleation can be observed in PL data at the onset of plastic relaxation.

Monotonous thermal PL quenching occurs even in coherent films with indirect bandgap.

Insights into recombination processes improve understanding of light emission in GeSn alloys.

Abstract

GeSn epitaxial heterostructures are emerging as prominent candidates for the monolithic integration of light sources on Si substrates. Here we propose a judicious explanation for their temperature-dependent photoluminescence (PL) that is based upon the so far disregarded optical activity of dislocations. By working at the onset of plastic relaxation, which occurs whenever the epilayer releases the strain accumulated during growth on the lattice mismatched substrate, we demonstrate that dislocation nucleation can be explicitly seen in the PL data. Notably, our findings point out that a monotonous thermal PL quenching can be observed in coherent films, in spite of the indirect nature of the GeSn bandgap. Our investigation, therefore, contributes to a deeper understanding of the recombination dynamics in this intriguing group IV alloy and offers insights into crucial phenomena shaping the light emission efficiency.