Degree Type

Dissertation

Date of Award

1993

Degree Name

Doctor of Philosophy

Department

Physics and Astronomy

First Advisor

Marshall Luban

Abstract

We solve the time-dependent Schrodinger equation for independent electrons in both periodic and aperiodic semiconductor superlattices with a superimposed static uniform electric field, F, using both analytical and numerical methods. In the case of periodic superlattices, in suitable circumstances the electron exhibits Bloch oscillations in the form of long-lived and virtually time-periodic sinusoidal center-of-mass oscillations. Depending on the miniband structure of the superlattice, the value of F, and the detailed form of the initial wave function, other dynamical phenomena can occur which can coexist with or even totally mask the Bloch oscillations. These include a nearly time-periodic coherent breathing mode, an unbounded acceleration of a portion of the electron wave packet antiparallel to the electric field, and high-frequency intra-well oscillations;With the introduction of an aperiodic potential term into the independent electron Hamiltonian, we find that the electron of course no longer exhibits time-periodic Bloch oscillations. Depending on the strength of the impurity potential, the miniband structure of the impurity-free superlattice, the value of F, and the initial wave function, the electron can exhibit almost-periodic oscillations, acceleration effects, intra-well oscillations, and Bloch-like oscillations of moderate lifetime which then give way to almost-periodic oscillations. We speculate that almost-periodic oscillations due to scattering from impurities could give rise to the rapid signal decay observed in recent experiments to detect Bloch oscillations in narrow-miniband superlattices. We propose that experiments based on wide-miniband superlattices may provide an opportunity to observe more Bloch-like oscillations than have ever been observed before.

DOI

https://doi.org/10.31274/rtd-180813-9597

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

Ann Marie Bouchard

Language

en

Proquest ID

AAI9334964

File Format

application/pdf

File Size

209 pages

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