Patents by Inventor Leo J. Schowalter

Leo J. Schowalter 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).

  • Defect reduction in seeded aluminum nitride crystal growth
    Patent number: 9771666
    Abstract: Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density?100 cm?2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.
    Type: Grant
    Filed: April 13, 2015
    Date of Patent: September 26, 2017
    Assignee: CRYSTAL IS, INC.
    Inventors: Robert T. Bondokov, Leo J. Schowalter, Kenneth Morgan, Glen A. Slack, Shailaja P. Rao, Shawn Robert Gibb
  • GROWTH OF LARGE ALUMINUM NITRIDE SINGLE CRYSTALS WITH THERMAL-GRADIENT CONTROL
    Publication number: 20170226661
    Abstract: In various embodiments, non-zero thermal gradients are formed within a growth chamber both substantially parallel and substantially perpendicular to the growth direction during formation of semiconductor crystals, where the ratio of the two thermal gradients (parallel to perpendicular) is less than 10, by, e.g., arrangement of thermal shields outside of the growth chamber.
    Type: Application
    Filed: January 20, 2017
    Publication date: August 10, 2017
    Inventors: Robert T. BONDOKOV, Shailaja P. RAO, Shawn Robert GIBB, Leo J. SCHOWALTER
  • DEFECT REDUCTION IN SEEDED ALUMINUM NITRIDE CRYSTAL GROWTH
    Publication number: 20170191184
    Abstract: Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density?100 cm?2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.
    Type: Application
    Filed: March 20, 2017
    Publication date: July 6, 2017
    Inventors: Robert T. Bondokov, Kenneth E. Morgan, Leo J. Schowalter, Glen A. Slack
  • PSEUDOMORPHIC ELECTRONIC AND OPTOELECTRONIC DEVICES HAVING PLANAR CONTACTS
    Publication number: 20170179336
    Abstract: In various embodiments, light-emitting devices incorporate smooth contact layers and polarization doping (i.e., underlying layers substantially free of dopant impurities) and exhibit high photon extraction efficiencies.
    Type: Application
    Filed: March 3, 2017
    Publication date: June 22, 2017
    Inventors: James R. Grandusky, Leo J. Schowalter, Muhammad Jamil, Mark C. Mendrick, Shawn R. Gibb
  • Ultraviolet light-emitting devices incorporating two-dimensional hole gases
    Patent number: 9680057
    Abstract: In various embodiments, light-emitting devices incorporate graded layers with compositional offsets at one or both end points of the graded layer to promote formation of two-dimensional carrier gases and polarization doping, thereby enhancing device performance.
    Type: Grant
    Filed: September 16, 2016
    Date of Patent: June 13, 2017
    Assignee: CRYSTAL IS, INC.
    Inventors: Craig Moe, James R. Grandusky, Shawn R. Gibb, Leo J. Schowalter, Kosuke Sato, Tomohiro Morishita
  • Defect reduction in seeded aluminum nitride crystal growth
    Patent number: 9670591
    Abstract: Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density ?100 cm?2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.
    Type: Grant
    Filed: August 13, 2014
    Date of Patent: June 6, 2017
    Assignee: CRYSTAL IS, INC.
    Inventors: Robert T. Bondokov, Kenneth E. Morgan, Leo J. Schowalter, Glen A. Slack
  • LARGE ALUMINUM NITRIDE CRYSTALS WITH REDUCED DEFECTS AND METHODS OF MAKING THEM
    Publication number: 20170145592
    Abstract: Reducing the microvoid (MV) density in AlN ameliorates numerous problems related to cracking during crystal growth, etch pit generation during the polishing, reduction of the optical transparency in an AlN wafer, and, possibly, growth pit formation during epitaxial growth of AlN and/or AlGaN. This facilitates practical crystal production strategies and the formation of large, bulk AlN crystals with low defect densities—e.g., a dislocation density below 104 cm?2 and an inclusion density below 104 cm?3 and/or a MV density below 104 cm?3.
    Type: Application
    Filed: February 8, 2017
    Publication date: May 25, 2017
    Inventors: Robert Bondokov, Kenneth E. Morgan, Glen A. Slack, Leo J. Schowalter
  • Defect reduction in seeded aluminum nitride crystal growth
    Patent number: 9624601
    Abstract: Bulk single crystal of aluminum nitride (AlN) having an areal planar defect density?100 cm?2. Methods for growing single crystal aluminum nitride include melting an aluminum foil to uniformly wet a foundation with a layer of aluminum, the foundation forming a portion of an AlN seed holder, for an AlN seed to be used for the AlN growth. The holder may consist essentially of a substantially impervious backing plate.
    Type: Grant
    Filed: August 13, 2014
    Date of Patent: April 18, 2017
    Assignee: CRYSTAL IS, INC.
    Inventors: Robert T. Bondokov, Kenneth E. Morgan, Leo J. Schowalter, Glen A. Stack
  • Pseudomorphic electronic and optoelectronic devices having planar contacts
    Patent number: 9620676
    Abstract: In various embodiments, light-emitting devices incorporate smooth contact layers and polarization doping (i.e., underlying layers substantially free of dopant impurities) and exhibit high photon extraction efficiencies.
    Type: Grant
    Filed: February 18, 2016
    Date of Patent: April 11, 2017
    Assignee: CRYSTAL IS, INC.
    Inventors: James R. Grandusky, Leo J. Schowalter, Muhammad Jamil, Mark C. Mendrick, Shawn R. Gibb
  • DOPED ALUMINUM NITRIDE CRYSTALS AND METHODS OF MAKING THEM
    Publication number: 20170084702
    Abstract: Fabrication of doped AlN crystals and/or AlGaN epitaxial layers with high conductivity and mobility is accomplished by, for example, forming mixed crystals including a plurality of impurity species and electrically activating at least a portion of the crystal.
    Type: Application
    Filed: November 10, 2016
    Publication date: March 23, 2017
    Inventors: Glen A. Slack, Leo J. Schowalter
  • ULTRAVIOLET LIGHT-EMITTING DEVICES INCORPORATING GRADED LAYERS AND COMPOSITIONAL OFFSETS
    Publication number: 20170084780
    Abstract: In various embodiments, light-emitting devices incorporate graded layers with compositional offsets at one or both end points of the graded layer to promote formation of two-dimensional carrier gases and polarization doping, thereby enhancing device performance.
    Type: Application
    Filed: September 16, 2016
    Publication date: March 23, 2017
    Inventors: Craig MOE, James R. GRANDUSKY, Shawn R. GIBB, Leo J. SCHOWALTER, Kosuke SATO, Tomohiro MORISHITA
  • ULTRAVIOLET LIGHT-EMITTING DEVICES INCORPORATING TWO-DIMENSIONAL HOLE GASES
    Publication number: 20170084779
    Abstract: In various embodiments, light-emitting devices incorporate graded layers with compositional offsets at one or both end points of the graded layer to promote formation of two-dimensional carrier gases and polarization doping, thereby enhancing device performance.
    Type: Application
    Filed: September 16, 2016
    Publication date: March 23, 2017
    Inventors: Craig MOE, James R. GRANDUSKY, Shawn R. GIBB, Leo J. SCHOWALTER, Kosuke SATO, Tomohiro MORISHITA
  • Large aluminum nitride crystals with reduced defects and methods of making them
    Patent number: 9598791
    Abstract: Reducing the microvoid (MV) density in AlN ameliorates numerous problems related to cracking during crystal growth, etch pit generation during the polishing, reduction of the optical transparency in an AlN wafer, and, possibly, growth pit formation during epitaxial growth of AlN and/or AlGaN. This facilitates practical crystal production strategies and the formation of large, bulk AlN crystals with low defect densities—e.g., a dislocation density below 104 cm?2 and an inclusion density below 104 cm?3 and/or a MV density below 104 cm?3.
    Type: Grant
    Filed: March 25, 2016
    Date of Patent: March 21, 2017
    Assignee: CRYSTAL IS, INC.
    Inventors: Robert Bondokov, Kenneth E. Morgan, Glen A. Slack, Leo J. Schowalter
  • Growth of large aluminum nitride single crystals with thermal-gradient control
    Patent number: 9580833
    Abstract: In various embodiments, non-zero thermal gradients are formed within a growth chamber both substantially parallel and substantially perpendicular to the growth direction during formation of semiconductor crystals, where the ratio of the two thermal gradients (parallel to perpendicular) is less than 10, by, e.g., arrangement of thermal shields outside of the growth chamber.
    Type: Grant
    Filed: April 15, 2015
    Date of Patent: February 28, 2017
    Assignee: CRYSTAL IS, INC.
    Inventors: Robert T. Bondokov, Shailaja P. Rao, Shawn R. Gibb, Leo J. Schowalter
  • Doped aluminum nitride crystals and methods of making them
    Patent number: 9525032
    Abstract: Fabrication of doped AlN crystals and/or AlGaN epitaxial layers with high conductivity and mobility is accomplished by, for example, forming mixed crystals including a plurality of impurity species and electrically activating at least a portion of the crystal.
    Type: Grant
    Filed: March 26, 2014
    Date of Patent: December 20, 2016
    Assignee: CRYSTAL IS, INC.
    Inventors: Glen A. Slack, Leo J. Schowalter
  • ALUMINUM NITRIDE BULK CRYSTALS HAVING HIGH TRANSPARENCY TO ULTRAVIOLET LIGHT AND METHODS OF FORMING THEM
    Publication number: 20160348273
    Abstract: In various embodiments, methods of forming single-crystal AN include providing a substantially undoped polycrystalline AN ceramic having an oxygen concentration less than approximately 100 ppm, forming a single-crystal bulk AN crystal by a sublimation-recondensation process at a temperature greater than approximately 2000 ° C., and cooling the bulk AN crystal to a first temperature between approximately 1500 ° C. and approximately 1800 ° C. at a first rate less than approximately 250 ° C./hour.
    Type: Application
    Filed: August 15, 2016
    Publication date: December 1, 2016
    Inventors: Sandra B. Schujman, Shailaja P. Rao, Robert T. Bondokov, Kenneth E. Morgan, Glen A. Slack, Leo J. Schowalter
  • Aluminum nitride bulk crystals having high transparency to untraviolet light and methods of forming them
    Patent number: 9447519
    Abstract: In various embodiments, methods of forming single-crystal AlN include providing a substantially undoped polycrystalline AlN ceramic having an oxygen concentration less than approximately 100 ppm, forming a single-crystal bulk AlN crystal by a sublimation-recondensation process at a temperature greater than approximately 2000° C., and cooling the bulk AlN crystal to a first temperature between approximately 1500° C. and approximately 1800° C. at a first rate less than approximately 250° C./hour.
    Type: Grant
    Filed: April 16, 2015
    Date of Patent: September 20, 2016
    Assignee: Crystal IS, Inc.
    Inventors: Sandra B. Schujman, Shailaja P. Rao, Robert T. Bondokov, Kenneth E. Morgan, Glen A. Slack, Leo J. Schowalter
  • Thick pseudomorphic nitride epitaxial layers
    Patent number: 9437430
    Abstract: Semiconductor structures are fabricated to include strained epitaxial layers exceeding a predicted critical thickness thereof.
    Type: Grant
    Filed: January 25, 2008
    Date of Patent: September 6, 2016
    Assignee: Crystal IS, Inc.
    Inventors: Leo J. Schowalter, Joseph A. Smart, James R. Grandusky, Shiwen Liu
  • PSEUDOMORPHIC ELECTRONIC AND OPTOELECTRONIC DEVICES HAVING PLANAR CONTACTS
    Publication number: 20160225949
    Abstract: In various embodiments, light-emitting devices incorporate smooth contact layers and polarization doping (i.e., underlying layers substantially free of dopant impurities) and exhibit high photon extraction efficiencies.
    Type: Application
    Filed: February 18, 2016
    Publication date: August 4, 2016
    Inventors: James R. Grandusky, Leo J. Schowalter, Muhammad Jamil, Mark C. Mendrick, Shawn R. Gibb
  • LARGE ALUMINUM NITRIDE CRYSTALS WITH REDUCED DEFECTS AND METHODS OF MAKING THEM
    Publication number: 20160208417
    Abstract: Reducing the microvoid (MV) density in AlN ameliorates numerous problems related to cracking during crystal growth, etch pit generation during the polishing, reduction of the optical transparency in an AlN wafer, and, possibly, growth pit formation during epitaxial growth of AlN and/or AlGaN. This facilitates practical crystal production strategies and the formation of large, bulk AlN crystals with low defect densities—e.g., a dislocation density below 104 cm?2 and an inclusion density below 104 cm?3 and/or a MV density below 104 cm?3.
    Type: Application
    Filed: March 25, 2016
    Publication date: July 21, 2016
    Inventors: Robert Bondokov, Kenneth E. Morgan, Glen A. Slack, Leo J. Schowalter