Magneto-Optical Characterization of Trions in Symmetric InP-Based Quantum Dots for Quantum Communication Applications.

Wojciech Rudno-Rudziński,Marek Burakowski,Mohamed Benyoucef,Johann P Reithmaier,Anna Musiał

doi:10.3390/ma14040942

Abstract

Magneto-optical parameters of trions in novel large and symmetric InP-based quantum dots, uncommon for molecular beam epitaxy-grown nanostructures, with emission in the third telecom window, are measured in Voigt and Faraday configurations of an external magnetic field. The diamagnetic coefficients are found to be in the range of 1.5–4 μeV/T2, and 8–15 μeV/T2, respectively out-of-plane and in-plane of the dots. The determined values of diamagnetic shifts are related to the anisotropy of dot sizes. Trion g-factors are measured to be relatively small, in the range of 0.3–0.7 and 0.5–1.3, in both configurations, respectively. Analysis of single carrier g-factors, based on the formalism of spin-correlated orbital currents, leads to similar values for hole and electron of ~0.25 for Voigt and ge ≈ −5; gh ≈ +6 for Faraday configuration of the magnetic field. Values of g-factors close to zero measured in Voigt configuration make the investigated dots promising for electrical tuning of the g-factor sign, required for schemes of single spin control in qubit applications.

Highlights

Self-assembled semiconductor quantum dots (QDs) constitute very interesting objects of study, both from the point of view of fundamental physics and various practical applications [1,2]
We focus our studies on charged excitons, because they may be unambiguously identified by magneto-optical spectroscopy and can be used to extract separately electron and hole g-factors in a Voigt configuration
For a typical molecular beam epitaxy (MBE)-grown InAs/InP QD system, the degree of anisotropy of dot shape translates into a value of a fine structure splitting (FSS) between two bright states of an exciton in the ground state on the order of at least tens of μeV, which can be clearly observed experimentally

Summary

Introduction

Self-assembled semiconductor quantum dots (QDs) constitute very interesting objects of study, both from the point of view of fundamental physics and various practical applications [1,2]. The value of the g-factor is strongly material-dependent already in bulk semiconductors [17], leading to large deviations from the value for free electrons of ge ≈ +2 It is further modified by the additional confinement of carriers in nanostructures, which is strong for QDs. the values of g-factors for a given QD system depend on the details of size, strain and material composition and their distribution within individual dots, as has been recently shown in the picture of spin-correlated orbital currents [18], which results i.a. in the anisotropy of g-factors, e.g., different values of g-factors in the directions perpendicular and parallel to the growth direction [19,20]. It makes it difficult to predict their values for new nanostructures, requiring experimental verification

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Conclusion