Highly uniform GaSb quantum dots with indirect-direct bandgap crossover at telecom range

TL;DR

This paper introduces GaSb quantum dots embedded in AlGaSb with a tunable indirect-direct bandgap crossover at telecom wavelengths, promising for quantum optics applications.

Contribution

It reports a novel growth method for uniform GaSb QDs with a bandgap crossover at telecom wavelengths, enabling new quantum photonic devices.

Findings

GaSb QDs exhibit an indirect-direct bandgap crossover at telecom wavelengths.

High material quality results in narrow spectral lines and low inhomogeneous broadening.

The QDs show potential for infrared quantum optics and photonic integration.

Abstract

We demonstrate a new quantum-confined semiconductor material based on GaSb quantum dots (QDs) embedded in single-crystalline AlGaSb matrix by filling droplet-etched nanoholes. The droplet-mediated growth mechanism allows formation of low QD densities required for non-classical single-QD light sources. The photoluminescence (PL) experiments reveal that the GaSb QDs have an indirect-direct bandgap crossover at telecom wavelengths. This is due to the alignment of the {\Gamma} and L valleys in the conduction band as a result of quantum confinement controlled by dimensions of the nanostructure. We show that in the direct bandgap regime close to 1.5 um wavelength, the GaSb QDs have a type I band alignment and exhibit excitonic emission with narrow spectral lines and very low inhomogeneous broadening of PL emission owing to the high material quality and dimensional uniformity. These properties are extremely promising in terms of applications in infrared quantum optics and quantum photonic integration.