Complex optical signatures from quantum dot nanostructures and behavior in inverted pyramidal recesses

G Juska,T H Chung,L O Mereni,B Van Hattem,P Corfdir,V Dimastrodonato,A Gocalinska,E Pelucchi,M Ediger

doi:10.1103/physrevb.89.205430

G Juska, T H Chung + Show 7 more

Open Access

https://doi.org/10.1103/physrevb.89.205430

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Abstract

A study of previously overlooked structural and optical properties of InGaAs heterostructures grown on (111)$B$ oriented GaAs substrates patterned with inverted 7.5-\ensuremath{\mu}m pitch pyramidal recesses is presented. First, the composition of the confinement barrier material (GaAs in this work) and its growth temperature are shown as some of the key parameters that determine the main quantum dot properties, including nontrivial emission energy dependence, excitonic pattern, and unusual photoluminescence energetic ordering of the InGaAs ensemble nanostructures. Second, the formation of a formerly unidentified type of InGaAs nanostructures---three corner quantum dots---is demonstrated in our structures next to the well-known ones (a quantum dot and three lateral quantum wires and quantum wells). The findings show the complexity of the pyramidal quantum dot system which strongly depends on the sample design and which should be considered when selecting highly symmetric (central) quantum dots in newly designed experimental projects.

Highlights

The practical realization of quantum information processing is still in its infancy.A number of possible implementations and different routes have been studied by the scientific community[1]
This implies that the Quantum dots (QDs) is no longer in direct physical contact with a vertical quantum wire (VQWR) and three vertical quantum wells (VQW)
The QD remains connected to only two other types of nanostructures of the same “nominal” alloy composition as the dot itself 20: three lateral quantum wires (LQWRs) and three lateral quantum wells (LQWs) [Figure 1(d) inset]

Summary

INTRODUCTION

The practical realization of quantum information processing is still in its infancy. A number of possible implementations and different routes have been studied by the scientific community[1]. We demonstrate that the optical properties of the InGaAs/GaAs system differ from that of the InGaAs/AlGaAs one, and that identification of a QD might not be trivial due to several peculiarities This complexity arises as (1) the main QD is not necessarily the least energetic feature in the whole spectrum as assumed until now, and (2) its emission can be confused with previously unidentified but usually present (at least in our pyramidal QD system) structures with QD-like photoluminescence. We refer to these structures as corner quantum dots (CQDs), and we demonstrate that they are a building block of the interconnecting nanostructure ensemble and not random features (e.g., due to random alloy disorder or segregation). The layout of the results representation in this paper is split into two parts: (1) the first one concentrating on the growth temperature dependent studies, (2) while the second one on the corner quantum dots

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RESULTS AND DISCUSSION

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Conclusions and summary