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       SEMINAR OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS
        Institute for Computational Sciences and Informatics
		CSI 929  (http://science.gmu.edu/physics)
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Exciton Calculations in Semiconductor Quantum Wells, Wires, and Dots
 
			   Scott N. Walck
			Naval Research Laboratory
			   Washington D. C.

Excitons, or electron-hole pairs, play a central role in the optical
properties of semiconductors, and their influence is even more
pronounced in confined geometries such as quantum wells, wires, and dots.
We calculate energies and wavefunctions for excitons in these
types of environments.  The exciton is described in the effective-mass
approximation by a two-body Hamiltonian which includes the electron
confinement, the hole confinement, and the electron-hole interaction.
Exciton binding energies are calculated using variational
techniques for quantum wells, rectangular quantum wires, and cylindrical
quantum dots.  These particular geometries have been the subject of
a systematic experimental investigation of the effect of confinement
and reduced dimensionality by our collaborators.  Their experiments
provide an indirect measure of binding energy as a function of nanostructure
feature size, and the agreement between theory and experiment is very good.
The effects of an external magnetic field on quantum-confined excitons
are also an area of current investigation.  In these calculations, the
"p-like" character of states at the top of the valence-band is important.
A formalism is used to calculate exciton energies and wavefunctions in
which the hole is described by the so-called Luttinger Hamiltonian.

	
                         Monday , February 12 1996
                                  5:00 pm
                          Room 206, Science & Tech. I
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