Fine Structure Splitting in QDs
Crystal Symmetry, Strain, and Piezo-Electricity		 Muhammad Usman, Shaikh Ahmed, Gerhard Klimeck

Objective:

  • Understand experimental data on QD spectra fine structure
  • Px and Py states are split in energy –
    Why – critical physical items

Approach:

  • Implement piezo-electric charges through electrostatic potential
  • Compare effects of
    • Crystal Symmetry
    • Strain
    • Piezoelectricity
  • Disk shaped dots d=10nm, h=2.5nm, 10nm cap, 20nm substrate, 0.6nm wetting layer

Impact:

  • Demonstrated quantitative agreement with experiment
  • Atomistic approach is essential

Impact:

  • •Crystal symmetry alone breaks symmetry of set of first excited states (weak)
  • Strain breaks symmetry stronger

    => effective mass, k.p fail!Piezoelectric effect opposes strain
  • => can flip orientation of the excited state

Publication:

  • Accepted in accepted in Springer Encyclopedia for Complexity, 2008 [J104].

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