Distributed Bragg reflector-mediated excitation of InAs/InP quantum dots emitting in the telecom C-band

TL;DR

This paper demonstrates a novel optical excitation mechanism for InAs/InP quantum dots using a distributed Bragg reflector, revealing carrier transfer effects that impact device coherence in telecom applications.

Contribution

It introduces a new excitation method mediated by a DBR and defect states, and analyzes its effects on carrier dynamics and emission properties of quantum dots.

Findings

Carrier transfer increases QD emission with temperature.

Carrier transfer affects the coherence of emitted photons.

Direct proof of carrier transfer via photoluminescence excitation spectrum.

Abstract

We demonstrate that optical excitation of InAs quantum dots (QDs) embedded directly in an InP matrix can be mediated via states in a quaternary compound constituting an InP/InGaAlAs bottom distributed Bragg reflector (DBR) and native defects in the InP matrix. It does not only change the carrier relaxation in the structure but could also lead to the imbalanced occupation of QDs with charge carriers, because the band structure favors the transfer of holes. Thermal activation of carrier transfer can be observed as an increase in the emission intensity versus temperature for excitation powers below saturation on the level of both an inhomogeneously broadened QD ensemble and single QD transitions. That increase in the QD emission is accompanied by a decrease in the emission from the InGaAlAs layer at low temperatures. Finally, carrier transfer between the InGaAlAs layer of the DBR and the InAs/InP QDs is directly proven by the photoluminescence excitation spectrum of the QD ensemble. The reported carrier transfer can increase the relaxation time of carriers into the QDs and thus be detrimental to the coherence properties of single and entangled photons. It is important to take it into account while designing QD-based devices.