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Highly Uniform InGaAs Pyramidal Quantum Dots with GaAs Barriers: Fine Structure Splitting

This research paper explores the physical properties of InGaAs pyramidal quantum dots with GaAs barriers, focusing on the fine structure splitting and their potential as tools for investigating low-dimensional solid state properties and developing new technologies and materials.

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Highly Uniform InGaAs Pyramidal Quantum Dots with GaAs Barriers: Fine Structure Splitting

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  1. Physical properties of highly uniform InGaAs Pyramidal Quantum Dots with GaAs barriers: the Fine Structure Splitting Lorenzo O. Mereni Valeria Dimastrodonato GediminasJuska Robert J. Young EmanuelePelucchi Epitaxy and Physics of Nanostructures Group: Tyndall National Institute University College of Cork Ireland

  2. Why Quantum Dots??? As Instruments of investigation for the properties of the low dimensional solid state As Development Tools for novel technologies and materials

  3. Characteristics of an ideal, easy-to-use QD source 1 - control over QD position and distance between QDs 2 - easy tunability of the QD electronic properties 3 - allow engineering of the coupling (i.e. allow the formation of artificial "molecules") and stacking of QDs in an easy and controllable way 4 - allow a single or stack of dots to be easily addressed and controlled electrically, and not only optically 5 - “identical” dots 6 - High optical quality

  4. SELF ASSEMBLED AND SITE CONTROLLED: TWO DIFFERENT APPROACHES Self assembled Site controlled

  5. WET LITHOGRAPHY GaAs (111)B substrate Resist deposited and exposed to UV light SiO2 GaAs SiO2 removal with HF Resistremoval Wet etching of tetrahedrical recesses Ready for growth!

  6. Easy patterning and growth process

  7. DOs AND DONTs OF PYRAMIDAL QUANTUM DOTS M. Baier, E. Pelucchi, S. Watanabe, and E. Kapon, “High-uniformity of site-controlled pyramidal quantum dots grown on pre-patterned substrates”, Appl. Phys. Lett. 84, 1943 (2004). M. Baier,et al...” Single photon emissionfrom site-controlled pyramidal quantum dots”, Appl. Phys. Lett. 84, 648 (2004). M. Baier, C. Constantin, E. Pelucchi, and E. Kapon, “Electroluminescence from a single pyramidal quantum dot in a light-emitting diode”, Appl. Phys. Lett. 84, 1967 (2004). +single photon electrically pumped…M.H..Baier et al unpublished

  8. InGaAs Dots with GaAs L. O. Mereni et al., Appl. Phys. Lett. 94, 223121 (2009) • Cladding Layer Al55%Ga45%As • GaAs barriers • Dot layer In25%Ga75%As – 0.5 nm nominal thickness • Vertical Quantum Wire σ = 1.2 meV FWHM = 2.8 meV

  9. CAN WE MAKE ENTANGLED PHOTONS WITH THESE DOTS?

  10. THE BIEXCITON-EXCITON CASCADE & FSS XX σ+ σ- H V Structural Asymmetries X FSS Alloy Disorder σ+ σ- V H Electric fields 0

  11. (111): AN IDEAL PLATFORM FOR THE DEVELOPMENT OF ENTANGLED PHOTONS • (111) Surfaces show a symmetry that has been indicated as ideal by many authors • K. F. Karlsson., to appear in Phys. Rev. B 81 • Schliwa et al., Phys. Rev. B 80, 161307 (2009) No Splitting is expected a priori for geometrical reasons from these dots The design of the dots itself is conceived to be free of structural aymmetries

  12. OPTICAL SETUP HALF WAVEPLATE LINEAR POLARIZER MONOCHROMATOR CLOSED CYCLE CRYOSTAT

  13. BUT…… X XX Mean FFS: 13 μeV σ = 4 μeV

  14. PHASE (μeV)

  15. FURTHER INVESTIGATIONS (μeV) Mean FFS: 13 μeV In0.25Ga0.65As 15% σ = 4 μeV Mean FFS: 20 μeV In0.35Ga0.65As σ = 10 μeV AlGaAs barriers Mean FFS: ? σ = ?

  16. Energy tuning (eV)

  17. DOTS WITH NITROGEN Small shift of the emission wavelenght Antibinding biexciton energy Splitting within the experimental error

  18. Thank you for your attention Slann

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