University of Illinois Urbana-Champaign

Luminescence studies of photoexcited electron-hole plasmas in silicon and germanium

Steranka, Frank Michael

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/2142/25305

Description

Title
Luminescence studies of photoexcited electron-hole plasmas in silicon and germanium
Author(s)
Steranka, Frank Michael
Issue Date
1985
Doctoral Committee Chair(s)
Wolfe, J.P.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • luminescence
  • photoexcited electron-hole plasmas
  • silicon
  • germanium
  • phonon wind
Language
en
Abstract
"This thesis presents the results of three studies of the photoluminescent properties of Si and Ge at low temperature. The first study is presented in Chapter 2 and deals with the transport of photoexcited electron-hole plasma (Ef:JP} in Si following pulsed laser excitation at temperatures below 50 K. The goal here was to determine the rate at which the photoexcited carriers expand fran the excitation surface into the crystal and. to determine the primary motive force. We found that for laser excitation levels up to the threshold for visible surface damage, the carriers moved away from the excitation region at velocities near or below the speed of sound. By imaging the expansion process, we found that under intense excitation levels the carriers were driven from the surface as a shell of plasma. Both of these facts point to a phonon-wind driven transport; phonons created in the hot-carrier thermalization process near the excitation region move ballistically into the crystal at low temperatures and drag the carriers with them i.e., the carriers are driven into the crystal by a ""phonon wind."" The second study, which is presented in Chapter 3, examines the equilibrium. properties of electron-hole liquid (EHL) in Ge as a function of uniaxial stress. This condensed phase of photoexcited carriers that forms in Ge and. Si has a high stability due to the degeneracies present in the band structure of the material. By applying <111> uniaxial stress to a Ge crystal, many of the degeneracies are lifted -altering the energetics of the system. We employed. both uniaxial-stress and strain-confinement geanetries to examine the changes in EHL density and. lifetime as a function of stress, and the results are compared to the results of many-body theoretical calculations. The third study is presented in Appendix A and consists of a detailed examination of the phase diagram of EHL in stressed Ge. When EHL condenses from a gas of free excitons (FE), t:NJ phase changes occur: the gas-liquid transition and an insulator-metal transition. By using a strain-confinement technique, we were able to observe the phase changes both spectrally and spatially. We fomxl evidence that the 1:N:I types of phase transition occurred separately within a small temperature range."
Type of Resource
text
Permalink
http://hdl.handle.net/2142/25305
Copyright and License Information
1985 Frank Michael Steranka

Owning Collections

Dissertations and Theses - Physics
Dissertations in Physics
Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois