Photo-produced phonons in semiconductors

The techniques of phonon imaging are used in conjunction with photoluminescence measurements to determine the characteristics of optically generated phonon sources in Si, Ge and GaAs at 1.7K. Focused-laser excitation of a semiconductor generates phonons as a byproduct of electronic excitation. A single carrier sheds this excess by the emission of optical phonons which cascade down in frequency, $\nu,$ by the normal anharmonic processes as they propagate in the crystal. This quasidiffusion of phonons is characterized by broad heat pulses at low excitation densities. At higher excitation densities carrier interactions may rapidly thermalize the excess carrier energy without optical phonon emission. The heated carrier distribution can directly emit low-$\nu$ acoustic phonons. The cross-over in energy relaxation mechanisms depends upon the continued production of high-$\nu$ phonons in the presence of a dense, cool plasma. The formation of such a plasma can be ascertained by observation of the electron-hole recombination luminescence.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Msall, Madeleine Elizabeth

Contributors dc:contributor

• Wolfe, J.P.

• Physics, Condensed Matter

Statement dc:rights

• Copyright 1995 Msall, Madeleine Elizabeth

Language dc:language

eng

Identifier

AAI9522154
(UMI)AAI9522154

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/20710