Channeling studies of the location of zinc in GaAs
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/sup 5/ 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 understanding 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.
- Research Organization:
- Illinois Univ., Urbana (USA)
- DOE Contract Number:
- AC02-76ER01198
- OSTI ID:
- 6184484
- Report Number(s):
- DOE/ER/01198-T35
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
GALLIUM ARSENIDES
X-RAY DIFFRACTION
ZINC
DIFFUSION
A CODES
ALUMINIUM COMPOUNDS
CHANNELING
CRYSTAL STRUCTURE
DATA ACQUISITION
DOPED MATERIALS
IMPURITIES
SAMPLE PREPARATION
TRANSMISSION ELECTRON MICROSCOPY
ARSENIC COMPOUNDS
ARSENIDES
COHERENT SCATTERING
COMPUTER CODES
DIFFRACTION
ELECTRON MICROSCOPY
ELEMENTS
GALLIUM COMPOUNDS
MATERIALS
METALS
MICROSCOPY
PNICTIDES
SCATTERING
360104* - Metals & Alloys- Physical Properties
656003 - Condensed Matter Physics- Interactions between Beams & Condensed Matter- (1987-)