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|Title:||Channeling studies of the location of zinc in gallium-arsenide|
|Author(s):||Christenson, Kurt Karl|
|Doctoral Committee Chair(s):||Brown, Frederick C.|
|Department / Program:||Physics|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Engineering, Electronics and Electrical
Physics, Condensed Matter
Engineering, Materials Science
|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 10$\sp5$ 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.
|Rights Information:||Copyright 1989 Christenson, Kurt Karl|
|Date Available in IDEALS:||2011-05-07|
|Identifier in Online Catalog:||AAI8916229|