Landolt-Börnstein - Group III Condensed Matter

CdSe/CdS and CdS/ZnSe intrinsic Stark superlattices

Abstract

This chapter talks about hexagonal CdSe/CdS and CdS/ZnSe strained-layer superlattices that have unusual properties due to their type-II band alignment and intrinsic piezo-electric fields, which are an order of magnitude larger than in comparable III-V superlattices. They are called intrinsic Stark superlattices because of the strong spatial separation of electrons and holes in a tilted band structure. Strained-layer superlattices (SLs) of CdSe/CdS are grown free standing on a hexagonal, relaxed buffer of CdS which is deposited on a (111)A GaAs substrate. The biaxial strain in both, CdS and CdSe layers, induced by the large lattice mismatch of 3.9% results in exceeded internal piezoelectric fields. Large intrinsic fields lead together with the type-II band alignment to a strongly tilted band structure which separates the electrons and holes into the CdS and CdSe layers, respectively. The calculated band structure as well as electron and hole wavefunctions for a symmetric CdSe/CdS SL are shown. A result of calculations of the density-dependence of the band structure, the transition energies and the wavefunction at high-density including screening as well as band-gap renormalization is shown. Stimulated emission in CdSe/CdS Stark superlattices is observed at high excitation conditions and attributed to transitions between higher subbands. Screening of the piezoelectric fields in CdS/ZnSe SLs leads to a spectral shift of up to 70 meV per decade change of excitation intensity. This chapter also includes transient effects and dynamics and references of intrinsic Stark superlattices.

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Title
CdSe/CdS and CdS/ZnSe intrinsic Stark superlattices
Book Title
Optical Properties. Part 2
In
Superlattices and coupled quantum-well structures of II-VI compounds
Book DOI
10.1007/b98078
Chapter DOI
10.1007/10860224_24
Part of
Landolt-Börnstein - Group III Condensed Matter
Volume
34C2
Editors
  • C. Klingshirn Send Email (10)
  • Editor Affiliation
  • 10 Institut für Angewandte Physik, Universität Karlsruhe (TH), 76131, Karlsruhe, Gemany
  • Authors
  • H. Kalt Send Email (101)
  • Author Affiliation
  • 101 Institut für Angewandte Physik, Universität Karlsruhe (TH), 76131, Karlsruhe, Gemany
  • Cite this content

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