Properties and Applications of Amorphous Gallium Arsenide Annealed to a Polycrystalline Form
Epple, John Henry
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https://hdl.handle.net/2142/80834
Description
Title
Properties and Applications of Amorphous Gallium Arsenide Annealed to a Polycrystalline Form
Author(s)
Epple, John Henry
Issue Date
2003
Doctoral Committee Chair(s)
Hsieh, K.C.
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
GaAs can be grown by Molecular Beam Epitaxy (MBE) in an amorphous form by lowering the growth temperature well below normal growth conditions. These growth conditions result in material that is very arsenic rich. When this material is annealed at moderate temperatures (400 to 500°C) it becomes polycrystalline and in some cases very conductive (rho = single digit mO-cm). Several aspects of the annealing were explored and annealing time, temperature, ambient, and ramp rate were all found to be important factors. Different conduction mechanisms were studied, and it was concluded that conduction is due to the formation of rhombohedral arsenic forming in between GaAs grains. These arsenic grains form a network around the GaAs grain structure, creating a conduction path through the material. Silicon doping of the amorphous GaAs lowers the amount of arsenic incorporation during growth. The silicon doped material has nearly the same resistivity as the undoped material when annealed but has a much better surface morphology. The phase change that this material goes through at a relatively low temperature makes it useful as an adhesion layer for wafer bonding. Using amorphous GaAs as an adhesion layer, GaAs substrates have been bonded to GaAs, InP, and glass at 400°C. MBE regrowths on bonded samples have shown moderate success.
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