Landolt-Börnstein - Group III Condensed Matter

7.4 Quantum wires and dots

Abstract

This chapter discusses the growth and spectroscopic characterization of quantum wires and dots. Due to the comparatively large acceptable dimensions of quantum structures in IV-VI materials, quantum wires and quantum dots can be made with photolithographic techniques. PbSe layers grown by MBE on BaF2 substrates are used. Photoluminescence spectra of a PbSe on BaF2 quantum wire array is given at 10K. Scanning transmission electron microscopy shows that the resulting particles are nearly spherical, with a narrow size distribution with mean diameters in the range from 2 to 15nm, and with lattice constants of the bulk material. Optical absorption spectra of PbSe quantum dots in a silicate glass gave evidence of expected energy levels. Quantum dots can be made "self-assembled" by molecular beam epitaxy with lattice mismatch. The quantum dots form by themselves, in order to reduce the total strain energy. The growth of self-assembled quantum dots is based on a marked difference of the lattice constants between two materials across a boundary. Atomic force microscopy (AFM) revealed the growth of layers with uniform dots of pyramidal shape. Elastic strain anisotropy was shown theoretically to explain that consecutive dot layers are grown both with lateral ordering due to in-plane interaction and with ordering in growth direction as well. Due to their high elasticity anisotropy, IV-VI materials should be ideally suited for the growth of self-assembled quantum dots.

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Title
7.4 Quantum wires and dots
Book Title
Optical Properties. Part 1
In
7 IV-VI Semiconductors
Book DOI
10.1007/b55683
Chapter DOI
10.1007/10479578_43
Part of
Landolt-Börnstein - Group III Condensed Matter
Volume
34C1
Editors
  • C. Klingshirn
  • Authors
  • M. Tacke
  • A. Ishida
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