Metalorganic Chemical Vapor Deposition of Gallium-Arsenide/aluminum-Gallium - Arsenide Thin-Layer Superlattices Andlaser Structures
Costrini, Gregory
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https://hdl.handle.net/2142/69330
Description
Title
Metalorganic Chemical Vapor Deposition of Gallium-Arsenide/aluminum-Gallium - Arsenide Thin-Layer Superlattices Andlaser Structures
Author(s)
Costrini, Gregory
Issue Date
1986
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, Electronics and Electrical
Abstract
Metalorganic chemical vapor deposition (MOCVD) is an open-tube vapor transport process ideally suited for the epitaxial growth of III-V semiconductors. The process utilizes the vapors of liquid metal alkyls as column III sources and gaseous hydrides as column V sources in an ultra-pure hydrogen carrier gas. High purity epitaxial layers of GaAs have been grown by MOCVD with residual impurity levels limited only by the purity of the metal alkyl/hydride source. Characterization data for growth of GaAs and Al(,x)Ga(,1-x)As, by MOCVD, are presented.
The pyrolysis reaction governing the growth of GaAs and Al(,x)Ga(,1-x)As by MOCVD is commonly believed to be simply diffusion limited in the temperature range of 600-750(DEGREES)C. Most previous analyses are extensions of studies of fluid flow at a rotating disk reactor and neglect thermal effects. In the work described here, experiments have been carried out in a vapor-phase vertical-flow rotating-disk reactor to investigate the influence of both hydrodynamic and thermal effects on the growth rate and uniformity of film deposition. This study indicates that susceptor temperature plays a key role in determining the nature of a complex boundary layer at the susceptor surface. This boundary layer determines both mass-transfer rates and thermal decomposition of the various reaction species and affects the relationship between the desired deposition and the parasitic effects of (1) spontaneous gas phase nucleation, (2) deposition elsewhere in the reactor and (3) unreacted species. In this paper, we describe the interrelationship of these effects and their influence on growth rate and uniformity of MOCVD grown GaAs.
The growth process can be described by a simple pyrolysis reaction that results only in deposition. The absence of competing etching reactions allows interfaces which are abrupt on a monatomic scale. High-resolution transmission electron micrographs of thin-layer GaAs/AlAs and GaAs/Al(,0.6)Ga(,0.4)As superlattices are provided for evidence of interface abruptness and thickness control of MOCVD.
The growth of Al(,x)Ga(,1-x)As by MOCVD, while not studied as extensively, has produced high quality material as demonstrated by double-heterostructure laser operation. Low-threshold laser operation of both the DH and graded-barrier quantum well laser structures is demonstrated. Both structures are used in the fabrication of an index-guided device, the self-aligned laser, using a two-step MOCVD growth technique.
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