## Files in this item

FilesDescriptionFormat

application/pdf

9124472.pdf (6MB)
(no description provided)PDF

## Description

 Title: High-frequency phonon propagation and detection in III-V semiconductors Author(s): Ramsbey, Mark Thomas Doctoral Committee Chair(s): Wolfe, J.P. Department / Program: Physics Discipline: Physics Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Physics, General Physics, Condensed Matter Abstract: Low temperature propagation and detection of high frequency acoustic phonons in GaAs and InAs is studied. Phonon imaging is used to study scattering of acoustic phonons in GaAs and angular dispersion of acoustic phonons in InAs. Photoluminescence spectroscopy is used to study the effects of nonequilibrium phonons on excitons in epitaxial semiconductors.The propagation of high frequency phonons through crystals at low temperatures is characterized by both ballistic and diffuse processes. Ballistic propagation of heat pulses is highly anisotropic due to phonon focusing. Experimental data is compared to Monte Carlo calculations and it is shown that the heat flux from phonons scattered a few times in the bulk retains a significant degree of anisotropy. The scattering rate of 0.7 THz phonons in GaAs is measured and a difference between the scattering of longitudinal and transverse modes is reported.The phonon focusing pattern changes with increasing phonon frequency due to angular dispersion. The results of frequency-selective phonon-focusing experiments on InAs are compared to Monte Carlo calculations incorporating Rigid Ion and Bond-Charge lattice dynamics models. The Bond-Charge model more accurately predicts the evolution of the phonon-focusing pattern in the frequency range investigated. Predictions of the focusing pattern for very high frequency phonons ($\nu$ $>$ 10$\sp{12}$ Hz) are presented.The intensity of lines associated with free and impurity-bound excitons in the photoluminescence spectrum of epitaxial GaAs changes with temperature even for T $<$ 2$\sp\circ$K. Similar spectral changes can be caused by nonequilibrium phonons created by a laser focused on the substrate crystal face. Experiments demonstrating the detection of nonequilibrium phonons propagating ballistically through the substrate are described. The possibilities of using this system as a detector for phonon-imaging experiments is discussed. Issue Date: 1991 Type: Text Language: English URI: http://hdl.handle.net/2142/20244 Rights Information: Copyright 1991 Ramsbey, Mark Thomas Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI9124472 OCLC Identifier: (UMI)AAI9124472
﻿