Optical and electronic properties of symmetric InAs/InGaAlAs/InP quantum dots formed by a ripening process in molecular beam epitaxy: a promising system for broad-range single-photon telecom emitters

TL;DR

This study investigates symmetric InAs quantum dots grown by ripening in molecular beam epitaxy, revealing broad near-infrared emission suitable for telecom applications, with insights into their optical properties and carrier dynamics.

Contribution

It provides detailed experimental and theoretical analysis of InAs/InAlGaAs/InP quantum dots with a novel growth process leading to broad emission spectra for telecom use.

Findings

Quantum dots exhibit broad emission from 1.4 to 2.0 μm.

Multimodal size distribution results from two-monolayer height differences.

PL lifetime is nearly dispersionless at approximately 1.3 ns.

Abstract

We present a detailed experimental optical study supported by theoretical modeling of InAs quantum dots (QDs) embedded in an InAlGaAs barrier lattice-matched to InP(001) grown with the use of a ripening step in molecular beam epitaxy. The method leads to the growth of in-plane symmetric QDs of low surface density, characterized by a multimodal size distribution resulting in a spectrally broad emission in the range of $1.4-2.0$ $\mu$m, essential for many near-infrared photonic applications. We find that, in contrast to the InAs/InP system, the multimodal distribution results here from a two-monolayer difference in QD height between consecutive families of dots. This may stem from the long-range ordering in the quaternary barrier alloy that stabilizes QD nucleation. Measuring the photoluminescence (PL) lifetime of the spectrally broad emission, we find a nearly dispersionless value of $1.3\pm0.3$ ns. Finally, we examine the temperature dependence of emission characteristics. We underline the impact of localized states in the wetting layer playing the role of carrier reservoir during thermal carrier redistribution. We determine the hole escape to the InAlGaAs barrier to be a primary PL quenching mechanism in these QDs.