This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/31230
Description
Title
Relaxation kinetics of excitons in cuprous oxide
Author(s)
O'Hara, Keith E.
Issue Date
1999
Doctoral Committee Chair(s)
Wolfe, J.P.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
relaxation kinetics
excitons
cuprous oxide
semiconductors
Bose-Einstein distributions
Language
en
Abstract
Cuprous oxide is a thoroughly s~udied semiconductor with long-lived, mobile
excitons. The kinetic energy distribution of the excitons is reproduced in phonon-assisted
luminescence spectra. When non-equilibrium excitons are produced by a laser pulse,
nanosecond-time-resolved luminescence reveals the relaxation of their kinetic energy
distribution.
It has been known for several years that, when the excitons are produced with the
highest attainable densities, the time-sequence of exciton kinetic energy distributions
closely resembles a sequence of Bose-Einstein distributions, with apparent temperatures
greater than that of the lattice. A widely used hypothesis is that the excitons exchange
energy through elastic collisions quickly enough to establish a quasi-equilibrium, with the
exciton gas having a temperature distinct from that of the lattice. The transient kinetic
energy distributions have thus been interpreted simply as quasi-equilibrium distributions,
with the gas density near enough the quantum density that the Bose statistics of the
excitons is noticeable.
This work is an experimental and theoretical study of such luminescence spectra. The
absolute brightness of the photoluminescence, compared with that of a known number of
excitons, indicates that the density of excitons is at all times too low to reveal their Bose
statistics-assuming they act as an ideal gas. The assumption of a quasi-equilibrium
among the excitons is abandoned, and the relaxation problem is treated through a
Boltzmann equation. Only relaxation processes which have been measured
experimentally are included: acoustic phonon emission and absorption, interconversion
between spin states, and non-radiative two-exciton decay. Numerical modeling
reproduces most of the experimental observations, without invoking Bose statistics.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
