Abstract

Improvements in growth and fabrication techniques in semiconductor physics have now made it possible to engineer quantum dots in which the electrons are confined in all three spatial directions. Electrons confined in these structures exhibit very different properties from those in quantum structures providing confinement in fewer dimensions. When an epitaxial layer is grown on a substrate of very different lattice constants under the correct conditions clusters form of dimensions comparable with the electron deBroglie wavelength. When these are structures are overgrown with a material of higher bandgap quantum dots are fabricated. These quantum structures are known as Self Assembled Quantum Dots (SAQDs). The three dimensional confinement results in discrete electron states unlike the continuum of states observed in unconfined structures. The discrete density of states (DOS) of a quantum dot has long been suggested to offer significant advantages in the production of both optical and electronic devices. The nature of the growth of SAQDs means that a large range of dot sizes are produced and this serves to destroy the discrete nature of the density of states function. The resulting (inhomogeneously) broadened DOS produce less favourable optical properties and therefore the challenge is produce SAQD with as little variation in size as possible.

© 2000 IEEE