Microanalysis and Characterization of Iii-v Heterostructures Grown by Metalorganic Chemical Vapor Deposition (Mocvd)
Jeng, Shwu-Jen
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https://hdl.handle.net/2142/71832
Description
Title
Microanalysis and Characterization of Iii-v Heterostructures Grown by Metalorganic Chemical Vapor Deposition (Mocvd)
Author(s)
Jeng, Shwu-Jen
Issue Date
1986
Department of Study
Metallurgy and Mining Engineering
Discipline
Metallurgical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Abstract
Metalorganic chemical vapor deposition (MOCVD) has been evolving as a major epitaxial technology. This technique has been used to prepare semiconductor heterostructures with abrupt interfaces and large-area growth uniformity. Much of the development of high speed electronic and optoelectronic devices is based on the MOCVD growth of sophisticated heterojunctions and circuits. In this study, high resolution electron microscopy (HREM), convergent beam electron diffraction (CBED), energy dispersive spectroscopy (EDS), and secondary ion mass spectrometry (SIMS) have been used for the characterization of heterojunction devices grown by MOCVD. The properties of III-V heterostructures have been studied in light of the observed interface structure, strain and defect content. The misfit dislocation theory proposed by Matthews has also been examined. The interfaces of GaAs/AlAs superlattices growth by MOCVD have been examined on the atomic scale and found to be extremely sharp for both the GaAs grown on AlAs and the AlAs grown on GaAs. The interface transition width is about one monolayer in both cases. For epitaxial growth of good quality, two-dimensional layer growth is preferred. Early stages of epitaxial growth of GaAs(,1-x)P(,x)/GaAs heterostructures shows that a two-dimensional layer growth is dominant up to a lattice mismatch of 1.4%. The measured critical thickness for misfit defect formation h(,c) is larger than that calculated by Matthews' model. The discrepancy may be due to an assumed oversimplified dislocation configuration, the large Peierls stress in the zinc-blende structure and the possible interfacial nucleation of mistfit defects. For two-dimensional layer growth, the most likely origin of misfit defect generation is the nucleation of defects at stress concentrators at either the surface or the interface. HOLZ line patterns from CBED have been used to determine the strains in SLS thin films. The lattice constants in the GaAs and GaAs(,0.8)P(,0.2) layers of the thin film SLS are different from those in the bulk. Structural analysis showns that a stable alloyed ohmic contact formed with 3 sec alloying at 430(DEGREES)C. The Ge-rich region has a tendency to recrystallize epitaxially on GaAs after alloying.
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