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Patent Issued for Zinc-Oxide Based Epitaxial Layers and Devices

July 23, 2014



By a News Reporter-Staff News Editor at Journal of Engineering -- Key Trans Investments, LLC (Dover, DE) has been issued patent number 8772829, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Adekore, Bunmi T. (Arlington, MA); Pierce, Jonathan (Somerset, NJ).

This patent was filed on November 22, 2010 and was published online on July 8, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "Chemical vapor deposition (CVD) is a deposition process that is used to form thin films on a substrate, such as a wafer. In a CVD process, a substrate is exposed to one or more precursors in a reaction chamber. The substrate is typically heated to a temperature higher than the decomposition temperature of the precursor so that when the precursor contacts the substrate it reacts with or decomposes onto the surface of the substrate to produce the desired thin film. However, the crystallographic structure of some substrates may affect the growth of the film, producing non-planar, three-dimensional films due to preferential growth rates along different crystallographic axes. For example, in hexagonal wurtzite materials, such as zinc oxide (ZnO), gallium nitride (GaN), and related materials, growth along the two dominant axes, the c-axis and a-axis, varies primarily due to the anisotropy in growth rates along these two axes. Some techniques have been developed to enable single crystalline and contiguous growth on the c-axis. See, e.g., PCT publication WO 2008/073469 (PCT application serial number PCT/US2007/025432, filed Dec. 11, 2007) entitled 'Zinc Oxide Multi-Junction Photovoltaic Cells and Optoelectronic Devices,' commonly owned by the assignee and incorporated by reference herein. Nevertheless, planar deposition of ZnO and ZnO based alloys on substrates with hexagonal crystallographic structures remains a challenge."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "In accordance with one embodiment of the invention, a method of growing a zinc-oxide based epitaxial layer includes providing an m-plane or vicinal m-plane wurtzite substrate, and forming a zinc-oxide based epitaxial layer on the substrate using metalorganic chemical vapor deposition.

"In accordance with related embodiments of the invention, the method may include heating the substrate between about 400.degree. C. to about 900.degree. C. The substrate may include a zinc-oxide based substrate. The metalorganic chemical vapor deposition supersaturation ratio of Group VI elements to Group II elements may be less than 8000. The zinc-oxide based epitaxial layer may further include gold, silver and/or potassium. The substrate may be a vicinal substrate having an off-cut angle from the m-plane ranging from about 2 degrees to about 15 degrees. The substrate may be heated between about 550.degree. C. to about 650.degree. C. Embodiments may include a device having an epitaxial layer produced according to the method.

"In accordance with another embodiment of the invention, a method of growing a zinc-oxide based epitaxial layer includes providing a vicinal wurtzite substrate having an off-cut angle from a principal plane ranging from about 2 degrees to about 15 degrees, heating the substrate, and forming a zinc-oxide based epitaxial layer on the substrate. The zinc-oxide based epitaxial layer may further include gold, silver and/or potassium. In accordance with related embodiments, the zinc-oxide based epitaxial layer may be formed using metalorganic chemical vapor deposition. The substrate may be a c-plane vicinal wurtzite substrate and may be heated between about 600.degree. C. to about 1000.degree. C., preferably between about 800.degree. C. to about 950.degree. C. The substrate may be an m-plane vicinal wurtzite substrate and may be heated between about 480.degree. C. to about 900.degree. C., preferably between about 550.degree. C. to about 650.degree. C. Embodiments may include a device having an epitaxial layer produced according to the method.

"In accordance with another embodiment of the invention, a method of growing a zinc-oxide based epitaxial layer includes providing an a-plane or vicinal a-plane wurtzite substrate, heating the substrate between about 400.degree. C. to about 900.degree. C., and forming a zinc-oxide based epitaxial layer, that further includes gold, silver and/or potassium, on the substrate. In accordance with related embodiments, the zinc-oxide based epitaxial layer may be formed using metalorganic chemical vapor deposition. The substrate may be a vicinal wurtzite substrate having an off-cut angle from the a-plane ranging from about 2 degrees to about 15 degrees. The substrate may be heated between about 550.degree. C. to about 650.degree. C. Embodiments may include a device having an epitaxial layer produced according to the method.

"In accordance with another embodiment of the invention, a device includes a zinc-oxide based epitaxial layer oriented along a non-polar (e.g., m-plane or a-plane) or vicinal non-polar plane of the zinc-oxide based epitaxial layer. The zinc-oxide based epitaxial layer may further include gold, silver and/or potassium. In accordance with another embodiment of the invention, a device includes a zinc-oxide based epitaxial layer oriented along a vicinal plane having an off-cut angle from a principal plane ranging from about 2 degrees to about 15 degrees, wherein the zinc-oxide based layer further comprises at least one element selected from the group consisting of gold, silver and potassium. In related embodiments, the device may include a light-emitting device and/or an LED exhibiting low droop during operation.

"In accordance with another embodiment of the invention, a method of growing a zinc-oxide based epitaxial layer includes providing a vicinal c-plane substrate having an off-cut angle from a principal plane ranging from about 2 degrees to about 15 degrees, heating the substrate, and forming a zinc-oxide based layer on the substrate.

"In accordance with another embodiment of the invention, a method of growing a zinc-oxide based epitaxial layer includes providing a semi-polar wurtzite substrate and forming a zinc-oxide based epitaxial layer on the substrate using metalorganic chemical vapor deposition. The method may include heating the substrate between about 400.degree. C. to about 900.degree. C. The substrate may include a zinc-oxide based substrate. The metalorganic chemical vapor deposition supersaturation ratio of Group VI elements to Group II elements may be less than 8000. The zinc-oxide based epitaxial layer may further include gold, silver and/or potassium. The substrate may have a deposition surface parallel or substantially parallel to a plane belonging to the {11-22} or {10-12} plane families. The method may include heating the substrate between about 550.degree. C. to about 650.degree. C. Embodiments may include a device having an epitaxial layer produced according to the method."

For the URL and additional information on this patent, see: Adekore, Bunmi T.; Pierce, Jonathan. Zinc-Oxide Based Epitaxial Layers and Devices. U.S. Patent Number 8772829, filed November 22, 2010, and published online on July 8, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8772829.PN.&OS=PN/8772829RS=PN/8772829

Keywords for this news article include: Chemistry, Zinc Oxide, Nanotechnology, Zinc Compounds, Emerging Technologies, Chemical Vapor Deposition, Key Trans Investments LLC.

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Source: Journal of Engineering


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