Selective oxidation of aluminum bearing III-V semiconductors with applications to quantum well heterostructure lasers
Maranowski, Steven Andrew
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Permalink
https://hdl.handle.net/2142/19519
Description
Title
Selective oxidation of aluminum bearing III-V semiconductors with applications to quantum well heterostructure lasers
Author(s)
Maranowski, Steven Andrew
Issue Date
1995
Doctoral Committee Chair(s)
Holonyak, Nick, Jr.
Department of Study
Electrical and Computer 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
Engineering, Materials Science
Language
eng
Abstract
In the present work, a water vapor oxidation process is used to convert high Al-composition $\rm Al\sb{x}Ga\sb{1-x}As\ and\ In\sb{0.5}(Al\sb{x}Ga\sb{1-x})\sb{0.5}P$ to stable, device-quality native oxides. The insulating and low-refractive-index properties of the native oxide prove useful in the fabrication of quantum well heterostructure laser diodes. The rate of oxide formation is sensitive to oxidation temperature and time, crystal doping, and, most dramatically the aluminum composition of the oxidizing layer. The higher aluminum composition semiconductors oxidize more readily.
"Selective oxidation of quantum well heterostructure crystals is used to convert only the highest aluminum composition materials to the native oxide. In the layered heterostructures commonly used in today's optoelectronic devices, selective oxidation is a unique way to ""bury"" an insulating and low-refractive-index oxide both above and below semiconductor layers used in a device. This makes possible, as described here, an edge-emitting laser diode that is confined both optically and electrically by ""buried"" oxide layers above and below the active region."
"Selective oxidation of $\rm Al\sb{x}Ga\sb{1-x}As$ occurs at low enough temperatures $(400\sp\circ$C-500$\sp\circ$C) to be performed on a fully metallized laser diode without adversely affecting its electrical performance. Metallized laser diodes are oxidized from their exposed facets, resulting in edge-emitting devices with current-blocking window regions at the mirrors. The buried oxide ""spike,"" which extends from the facet into the crystal, forms selectively in a region of high aluminum composition. The buried oxide removes the current injection from the facet region, protects the facet, and results in improved maximum output powers from the lasers."
Finally, the ability to form low-index $\rm(n\sim1.55)$ layers of oxide between high-index semiconductor crystals facilitates the formation of high-index-contrast distributed Bragg reflecting (DBR) mirrors. The properties of these mirrors and their applications to vertical cavity surface emitting lasers and edge-emitting lasers are described.
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