Information Technology Reference
In-Depth Information
Fig. 8.3 Experimental semiconductor implementation of a quantum dot
Fig. 8.4 Band structure of
a semiconductor containing
a quantum dot
crystal lattices. If the deposition continues, they grow, making formation of indi-
vidual “drops” on the surface of the first layer (called the “wetting” layer) more
advantageous than the uniform distribution of matter on the surface of the first
layer. Thus little “pyramids” with the properties of quantum dots arise (Fig.
8.3
).
Qualitatively, these pyramids can be regarded as defects on the surface of the
semiconductor core. In this case impurity levels appear in the band structure
(Fig.
8.4
)—slightly above the valence band (holes) and slightly below the conduc-
tion band (electrons). Levels corresponding to the impurity level of the conduction
band are characterized by a discrete spectrum, i.e., they correspond to the quantum
dot.
The unique properties of quantum dots laid the foundation of the concept of
building semiconductor information processing tools—cellular automata—devel-
oped by a team of physicists at the University of Notre Dame (France).
