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|Title:||Low Temperature Electron Irradiation Induced Defects in Gallium-Arsenide: Bulk and Surface Acoustic Wave Studies|
|Author(s):||Brophy, Martin Joseph, Jr.|
|Department / Program:||Physics|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Physics, Condensed Matter|
|Abstract:||Irradiation of GaAs with 2.25 - 2.5 MeV electrons at temperatures below 190 K produces two peaks in ultrasonic attenuation versus temperature. The defects responsible for both peaks have trigonal symmetry and were observed in n-type and semi-insulating GaAs with bulk and surface acoustic waves (SAW) respectively. Bulk waves at eight frequencies between 9 and 130 MHz and SAW at 73 and 145 MHz were used. The reorientation kinetics of both peaks follow the Arrhenius law.
The annealing of both peaks was studied with isochronal and isothermal anneals in the temperature range 200 - 335 K. Peak I anneals with a spectrum of activation energies in the range .7 - 1.1 eV between 220 and 335 K. Peak II anneals with a single activation energy of about 1.1 eV above 300 K. The different annealing characteristics indicate that these peaks represent two distinct defects. The annealing above 300 K has not been seen in electrical resistivity measurements, but was observed in earlier length change experiments.
Irradiation of GaAs:Cr produces no Cr-radiation defect complexes. The attenuation peak associated with Cr('2+) decrease with electron dose, but starts to recover at 150 K. The same behavior is observed when the sample is illuminated with white light, indicating that ionization and not complex formation lowers the Cr('2+) peak height. The Cr('2+) relaxation is observed to proceed without a direct process, but can be fit well with a two exponential process.
The implications of our results in the context of previous work by others is discussed, and some preliminary speculation is made regarding the provenance of the attenuation peaks observed.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2015-05-13|