Lateral interdot coupling among dense ensemble of InAs quantum dots grown on InP substrate observed at cryogenic temperatures

A Maryński,J Misiewicz,M Gawełczyk,V Liverini,G SȩK,M Syperek,M Beck,J Faist,M Pieczarka

doi:10.1088/1742-6596/906/1/012008

Abstract

The lateral interdot coupling is investigated in high density (∼10 cm−2 ) self-assembled InAs quantum dots (QDs) grown on an InP substrate. Two types of structures are selected for this study, in which QDs are embedded into an InAlAs matrix, forming nearly twice stronger confinement for an electron and a hole than expected for an InAlGaAs counterpart. Resonantly injected low carrier population in these families of QDs gives very different spectral and temporal response in the temperature range of 5-30 K. While InAs/InAlGaAs QDs show monotonic temperature quench of photoluminescence (PL), the process seems to be ineffective in the family of InAs/InAlAs dots. Moreover, the PL decay traces for InAs/InAlGaAs QDs reveal a two-exponential decay as compared to a mono-exponential one observed for InAs/InAlAs dots. While a short decay component of ≤1.9 ns has been attributed to recombination of an electron-hole pair confined in the dot, the long one of >2.4 ns, observed exclusively for InAs/InGaAlAs QDs, is attributed to recombination of spatially separated electron-hole pairs formed due to carrier exchange between adjacent dots.

Highlights

The presence of lateral coupling among high surface density self-assembled quantum dots (QDs) in the absence of external electric field has been studied for many years, in the view of the appropriate description of the temperature activated carrier transfer process.[1, 2] At high temperatures, such processes can be well described with a carrier activation mechanism enhanced by a large density of phonon states that allows efficient carrier redistribution via higher order QDs states or the wetting layer (WL)
To look for the phenomenon of the lateral interdot carrier coupling at cryogenic temperatures the attention has been focused on InAs QDs grown on an InP(001) substrate, devoted for the laser applications in the third telecom spectral window (1.55 μm)
The absorption edge of the wetting layer is observed in the photoluminescence excitation (PLE) experiments at ∼0.98 eV and ∼1.02 eV for QD structures with a quaternary and ternary barrier, respectively

Summary

Introduction

The presence of lateral coupling among high surface density self-assembled quantum dots (QDs) in the absence of external electric field has been studied for many years, in the view of the appropriate description of the temperature activated carrier transfer process.[1, 2] At high temperatures, such processes can be well described with a carrier activation mechanism enhanced by a large density of phonon states that allows efficient carrier redistribution via higher order QDs states or the wetting layer (WL). The lateral interdot coupling is investigated in high density (∼1011 cm−2) selfassembled InAs quantum dots (QDs) grown on an InP substrate.

Results

Conclusion