University of Illinois Urbana-Champaign

Channeling studies of the location of zinc in GaAs

Christenson, Kurt Karl

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https://hdl.handle.net/2142/23931

Description

Title
Channeling studies of the location of zinc in GaAs
Author(s)
Christenson, Kurt Karl
Issue Date
1989
Doctoral Committee Chair(s)
Eades, J.A.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Diffusion of Zinc in Gallium Arsenide (GaAs)
  • Diffusion Coefficient
  • Fick's Law
  • Zinc Doping
  • Channeling Studies
Language
en
Abstract
The diffusion of zinc in GaAs is highly anomalous in that the diffusion coefficient (D) is proportional to the zinc concentration squared in marked contrast to Fick's law which predicts that D is concentration independent. D is also very sensitive to the ambient conditions during diffusion, particularly the arsenic overpressure and the presence of other doping species. Further, heavy zinc doping can increase the self diffusion rates for gallium and aluminum by 105 and is thus useful for selectively ,disordering GaAs/GaAlAs layer structures. The diffusion mechanisms involved are poorly understood, particularly the experimental finding that the column V sites (As, P and Sb) are not disordered. We believe that the anomalous nature can be explained by combining the theories of R. L. Longini (1962) on the effect of the hole density on the interstitial population and of K. Weiser (1962) on the effect of the charge state of an interstitial on the diffusion activation energy. To test our hypothesis, we have located the position of the zinc in the GaAs lattice with the ALCHEMI technique (Atom Location by CHanneling Enhanced Microanalysis) in a Transmission Electron Microscope (TEM). This required substantial enhancements to the x-ray microanalytic abilities of the TEM along with an improved understand of the nature of the illumination in the immersion lens of a TEM, all of which are discussed. Our results indicate that, within the experimental error, all of the zinc occupies the gallium sites which is consistent with our hypothesis. Further research involving TEM, synchrotron, diffusion and device studies are also suggested.
Type of Resource
text
Permalink
http://hdl.handle.net/2142/23931
Copyright and License Information
1989 Kurt Karl Christenson

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