Patents by Inventor Valeri F. Tsvetkov
Valeri F. Tsvetkov has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Publication number: 20220403552Abstract: Silicon carbide (SiC) crystalline materials and related methods are disclosed that provide SiC crystalline materials with reduced optical absorption. In certain aspects, SiC crystalline materials with reduced absorption coefficients for wavelengths of light within the visible spectrum are disclosed. Various peaks in absorption over a wavelength spectrum may be reduced in SiC crystalline materials to improve overall absorption coefficient uniformity across the visible spectrum. By providing such improvements in absorption coefficients for SiC crystalline materials, reduced reflection and transmission losses of light in corresponding devices may be realized. Related methods are disclosed that include various combinations of crystalline growth, with and without various post-growth thermal conditioning steps.Type: ApplicationFiled: June 17, 2021Publication date: December 22, 2022Inventors: Robert Tyler Leonard, Elif Balkas, Valeri F. Tsvetkov, Yuri Khlebnikov, Kathryn A. O'Hara, Simon Bubel, David P. Malta
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Publication number: 20220189768Abstract: Silicon carbide (SiC) materials including SiC wafers and SiC boules and related methods are disclosed that provide large dimension SiC wafers with reduced crystallographic stress. Growth conditions for SiC materials include maintaining a generally convex growth surface of SiC crystals, adjusting differences in front-side to back-side thermal profiles of growing SiC crystals, supplying sufficient source flux to allow commercially viable growth rates for SiC crystals, and reducing the inclusion of contaminants or non-SiC particles in SiC source materials and corresponding SiC crystals. By forming larger dimension SiC crystals that exhibit lower crystallographic stress, overall dislocation densities that are associated with missing or additional planes of atoms may be reduced, thereby improving crystal quality and usable SiC crystal growth heights.Type: ApplicationFiled: December 15, 2020Publication date: June 16, 2022Inventors: Yuri Khlebnikov, Varad R. Sakhalkar, Caleb A. Kent, Valeri F. Tsvetkov, Michael J. Paisley, Oleksandr Kramarenko, Matthew David Conrad, Eugene Deyneka, Steven Griffiths, Simon Bubel, Adrian R. Powell, Robert Tyler Leonard, Elif Balkas, Curt Progl, Michael Fusco, Alexander Shveyd, Kathy Doverspike, Lukas Nattermann
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Publication number: 20210198804Abstract: Silicon carbide (SiC) wafers and related methods are disclosed that include large diameter SiC wafers with wafer shape characteristics suitable for semiconductor manufacturing. Large diameter SiC wafers are disclosed that have reduced deformation related to stress and strain effects associated with forming such SiC wafers. As described herein, wafer shape and flatness characteristics may be improved by reducing crystallographic stress profiles during growth of SiC crystal boules or ingots. Wafer shape and flatness characteristics may also be improved after individual SiC wafers have been separated from corresponding SiC crystal boules. In this regard, SiC wafers and related methods are disclosed that include large diameter SiC wafers with suitable crystal quality and wafer shape characteristics including low values for wafer bow, warp, and thickness variation.Type: ApplicationFiled: December 17, 2020Publication date: July 1, 2021Inventors: Yuri Khlebnikov, Varad R. Sakhalkar, Caleb A. Kent, Valeri F. Tsvetkov, Michael J. Paisley, Oleksandr Kramarenko, Matthew David Conrad, Eugene Deyneka, Steven Griffiths, Simon Bubel, Adrian R. Powell, Robert Tyler Leonard, Elif Balkas, Jeffrey C. Seaman
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Patent number: 9790619Abstract: A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system by reducing the separation between a silicon carbide seed crystal and a seed holder until the conductive heat transfer between the seed crystal and the seed holder dominates the radiative heat transfer between the seed crystal and the seed holder over substantially the entire seed crystal surface that is adjacent the seed holder.Type: GrantFiled: July 12, 2011Date of Patent: October 17, 2017Assignee: Cree, Inc.Inventors: Robert Tyler Leonard, Adrian Powell, Valeri F. Tsvetkov
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Patent number: 9200381Abstract: A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system by reducing the separation between a silicon carbide seed crystal and a seed holder until the conductive heat transfer between the seed crystal and the seed holder dominates the radiative heat transfer between the seed crystal and the seed holder over substantially the entire seed crystal surface that is adjacent the seed holder.Type: GrantFiled: October 12, 2005Date of Patent: December 1, 2015Assignee: Cree, Inc.Inventors: Robert Tyler Leonard, Adrian Powell, Valeri F. Tsvetkov
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Patent number: 9059118Abstract: A method is disclosed for producing high quality semi-insulating silicon carbide crystals in the absence of relevant amounts of deep level trapping elements. The invention includes the steps of heating a silicon carbide crystal having a first concentration of point defects to a temperature that thermodynamically increases the number of point defects and resulting states in the crystal, and then cooling the heated crystal at a sufficiently rapid rate to maintain an increased concentration of point defects in the cooled crystal.Type: GrantFiled: June 24, 2009Date of Patent: June 16, 2015Assignee: Cree, Inc.Inventors: Jason Ronald Jenny, David Phillip Malta, Hudson McDonald Hobgood, Stephan Mueller, Valeri F. Tsvetkov
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Patent number: 8785946Abstract: A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1 c screw dislocation density from about 500 cm?2 to about 2000 cm?2.Type: GrantFiled: February 26, 2013Date of Patent: July 22, 2014Assignee: Cree, Inc.Inventors: Adrian Powell, Mark Brady, Stephan G. Mueller, Valeri F. Tsvetkov, Robert T. Leonard
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Patent number: 8624267Abstract: A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1 c screw dislocation density from about 500 cm?2 to about 2000 cm?2.Type: GrantFiled: February 26, 2013Date of Patent: January 7, 2014Assignee: Cree, Inc.Inventors: Adrian Powell, Mark Brady, Stephan G. Mueller, Valeri F. Tsvetkov, Robert T. Leonard
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Patent number: 8618553Abstract: A process is described for producing silicon carbide crystals having increased minority carrier lifetimes. The process includes the steps of heating and slowly cooling a silicon carbide crystal having a first concentration of minority carrier recombination centers such that the resultant concentration of minority carrier recombination centers is lower than the first concentration.Type: GrantFiled: August 30, 2010Date of Patent: December 31, 2013Assignee: Cree, Inc.Inventors: Calvin H. Carter, Jr., Jason R. Jenny, David P. Malta, Hudson M. Hobgood, Valeri F. Tsvetkov, Mrinal K. Das
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Patent number: 8384090Abstract: A high quality single crystal wafer of SiC is disclosed having a diameter of at least about 3 inches and a 1c screw dislocation density of less than about 2000 cm?2.Type: GrantFiled: November 15, 2007Date of Patent: February 26, 2013Assignee: Cree, Inc.Inventors: Adrian Powell, Mark Brady, Stephan G. Mueller, Valeri F. Tsvetkov, Robert T. Leonard
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Publication number: 20120167825Abstract: A physical vapor transport growth technique for silicon carbide is disclosed. The method includes the steps of introducing a silicon carbide powder and a silicon carbide seed crystal into a physical vapor transport growth system, separately introducing a heated silicon-halogen gas composition into the system in an amount that is less than the stoichiometric amount of the silicon carbide source powder so that the silicon carbide source powder remains the stoichiometric dominant source for crystal growth, and heating the source powder, the gas composition, and the seed crystal in a manner that encourages physical vapor transport of both the powder species and the introduced silicon-halogen species to the seed crystal to promote bulk growth on the seed crystal.Type: ApplicationFiled: February 21, 2012Publication date: July 5, 2012Inventors: STEPHAN G. MUELLER, HUDSON M. HOBGOOD, VALERI F. TSVETKOV
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Patent number: 8163086Abstract: A physical vapor transport growth technique for silicon carbide is disclosed. The method includes the steps of introducing a silicon carbide powder and a silicon carbide seed crystal into a physical vapor transport growth system, separately introducing a heated silicon-halogen gas composition into the system in an amount that is less than the stoichiometric amount of the silicon carbide source powder so that the silicon carbide source powder remains the stoichiometric dominant source for crystal growth, and heating the source powder, the gas composition, and the seed crystal in a manner that encourages physical vapor transport of both the powder species and the introduced silicon-halogen species to the seed crystal to promote bulk growth on the seed crystal.Type: GrantFiled: August 29, 2007Date of Patent: April 24, 2012Assignee: Cree, Inc.Inventors: Stephan G. Mueller, Hudson M. Hobgood, Valeri F. Tsvetkov
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Patent number: 8147991Abstract: A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system by reducing the separation between a silicon carbide seed crystal and a seed holder until the conductive heat transfer between the seed crystal and the seed holder dominates the radiative heat transfer between the seed crystal and the seed holder over substantially the entire seed crystal surface that is adjacent the seed holder.Type: GrantFiled: May 3, 2010Date of Patent: April 3, 2012Assignee: Cree, Inc.Inventors: Jason Ronald Jenny, David Phillip Malta, Hudson McDonald Hobgood, Stephan Georg Mueller, Mark Brady, Robert Tyler Leonard, Adrian Powell, Valeri F. Tsvetkov
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Publication number: 20110290174Abstract: A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system by reducing the separation between a silicon carbide seed crystal and a seed holder until the conductive heat transfer between the seed crystal and the seed holder dominates the radiative heat transfer between the seed crystal and the seed holder over substantially the entire seed crystal surface that is adjacent the seed holder.Type: ApplicationFiled: July 12, 2011Publication date: December 1, 2011Applicant: NAVY, SECRETARY OF THE, UNITED STATES OF AMERICAInventors: Robert Tyler Leonard, Adrian Powell, Valeri F. Tsvetkov
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Patent number: 7943954Abstract: A semiconductor light emitting diode includes a semiconductor substrate, an epitaxial layer of n-type Group III nitride on the substrate, a p-type epitaxial layer of Group III nitride on the n-type epitaxial layer and forming a p-n junction with the n-type layer, and a resistive gallium nitride region on the n-type epitaxial layer and adjacent the p-type epitaxial layer for electrically isolating portions of the p-n junction. A metal contact layer is formed on the p-type epitaxial layer. In method embodiments disclosed, the resistive gallium nitride border is formed by forming an implant mask on the p-type epitaxial region and implanting ions into portions of the p-type epitaxial region to render portions of the p-type epitaxial region semi-insulating. A photoresist mask or a sufficiently thick metal layer may be used as the implant mask.Type: GrantFiled: July 22, 2009Date of Patent: May 17, 2011Assignee: Cree, Inc.Inventors: Yifeng Wu, Gerald H. Negley, David B. Slater, Jr., Valeri F. Tsvetkov, Alexander Suvorov
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Publication number: 20110024766Abstract: A method is disclosed for producing a high quality bulk single crystal of silicon carbide in a seeded growth system by reducing the separation between a silicon carbide seed crystal and a seed holder until the conductive heat transfer between the seed crystal and the seed holder dominates the radiative heat transfer between the seed crystal and the seed holder over substantially the entire seed crystal surface that is adjacent the seed holder.Type: ApplicationFiled: May 3, 2010Publication date: February 3, 2011Applicant: Cree, Inc.Inventors: Jason Ronald Jenny, David Phillip Malta, Hudson McDonald Hobgood, Stephan Georg Mueller, Mark Brady, Robert Tyler Leonard, Adrian Powell, Valeri F. Tsvetkov
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Publication number: 20100320477Abstract: A process is described for producing silicon carbide crystals having increased minority carrier lifetimes. The process includes the steps of heating and slowly cooling a silicon carbide crystal having a first concentration of minority carrier recombination centers such that the resultant concentration of minority carrier recombination centers is lower than the first concentration.Type: ApplicationFiled: August 30, 2010Publication date: December 23, 2010Applicant: CREE, INC.Inventors: Calvin H. Carter, JR., Jason R. Jenny, David P. Malta, Hudson M. Hobgood, Valeri F. Tsvetkov, Mrinal K. Das
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Patent number: 7811943Abstract: A process is described for producing silicon carbide crystals having increased minority carrier lifetimes. The process includes the steps of heating and slowly cooling a silicon carbide crystal having a first concentration of minority carrier recombination centers such that the resultant concentration of minority carrier recombination centers is lower than the first concentration.Type: GrantFiled: February 7, 2005Date of Patent: October 12, 2010Assignee: Cree, Inc.Inventors: Calvin H. Carter, Jr., Jason R. Jenny, David P. Malta, Hudson M. Hobgood, Valeri F. Tsvetkov, Mrinal K. Das
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Publication number: 20090309124Abstract: A semiconductor light emitting diode includes a semiconductor substrate, an epitaxial layer of n-type Group III nitride on the substrate, a p-type epitaxial layer of Group III nitride on the n-type epitaxial layer and forming a p-n junction with the n-type layer, and a resistive gallium nitride region on the n-type epitaxial layer and adjacent the p-type epitaxial layer for electrically isolating portions of the p-n junction. A metal contact layer is formed on the p-type epitaxial layer. In method embodiments disclosed, the resistive gallium nitride border is formed by forming an implant mask on the p-type epitaxial region and implanting ions into portions of the p-type epitaxial region to render portions of the p-type epitaxial region semi-insulating. A photoresist mask or a sufficiently thick metal layer may be used as the implant mask.Type: ApplicationFiled: July 22, 2009Publication date: December 17, 2009Applicant: CREE, INC.Inventors: Yifeng Wu, Gerald H. Negley, David B. Slater, JR., Valeri F. Tsvetkov, Alexander Suvorov
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Publication number: 20090256162Abstract: A method is disclosed for producing high quality semi-insulating silicon carbide crystals in the absence of relevant amounts of deep level trapping elements. The invention includes the steps of heating a silicon carbide crystal having a first concentration of point defects to a temperature that thermodynamically increases the number of point defects and resulting states in the crystal, and then cooling the heated crystal at a sufficiently rapid rate to maintain an increased concentration of point defects in the cooled crystal.Type: ApplicationFiled: June 24, 2009Publication date: October 15, 2009Applicant: CREE, INC.Inventors: Jason Ronald Jenny, David Phillip Malta, Hudson McDonald Hobgood, Stephan Mueller, Valeri F. Tsvetkov