Patents by Inventor Umesh K. Mishra

Umesh K. Mishra 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).

  • Publication number: 20100187555
    Abstract: An (Al, Ga, In)N and ZnO direct wafer bonded light emitting diode (LED), wherein light passes through electrically conductive ZnO. Flat and clean surfaces are prepared for both the (Al, Ga, In)N and ZnO wafers. A wafer bonding process is then performed between the (Al, Ga, In)N and ZnO wafers, wherein the (Al, Ga, In)N and ZnO wafers are joined together and then wafer bonded in a nitrogen ambient under uniaxial pressure at a set temperature for a set duration. After the wafer bonding process, ZnO is shaped for increasing light extraction from inside of LED.
    Type: Application
    Filed: April 1, 2010
    Publication date: July 29, 2010
    Applicants: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA, JAPAN SCIENCE AND TECHNOLOGY AGENCY
    Inventors: Akihiko Murai, Christina Ye Chen, Daniel B. Thompson, Lee S. McCarthy, Steven P. DenBaars, Shuji Nakamura, Umesh K. Mishra
  • Patent number: 7737451
    Abstract: An LED made from a wide band gap semiconductor material and having a low resistance p-type confinement layer with a tunnel junction in a wide band gap semiconductor device is disclosed. A dissimilar material is placed at the tunnel junction where the material generates a natural dipole. This natural dipole is used to form a junction having a tunnel width that is smaller than such a width would be without the dissimilar material. A low resistance p-type confinement layer having a tunnel junction in a wide band gap semiconductor device may be fabricated by generating a polarization charge in the junction of the confinement layer, and forming a tunnel width in the junction that is smaller than the width would be without the polarization charge. Tunneling through the tunnel junction in the confinement layer may be enhanced by the addition of impurities within the junction. These impurities may form band gap states in the junction.
    Type: Grant
    Filed: February 23, 2006
    Date of Patent: June 15, 2010
    Assignee: Cree, Inc.
    Inventors: James P. Ibbetson, Bernd P. Keller, Umesh K. Mishra
  • Patent number: 7728356
    Abstract: An enhancement mode High Electron Mobility Transistor (HEMT) comprising a p-type nitride layer between the gate and a channel of the HEMT, for reducing an electron population under the gate. The HEMT may also comprise an Aluminum Nitride (AlN) layer between an AlGaN layer and buffer layer of the HEMT to reduce an on resistance of a channel.
    Type: Grant
    Filed: June 2, 2008
    Date of Patent: June 1, 2010
    Assignee: The Regents of the University of California
    Inventors: Chang Soo Suh, Umesh K. Mishra
  • Patent number: 7723216
    Abstract: A method for growing reduced defect density planar gallium nitride (GaN) films is disclosed. The method includes the steps of (a) growing at least one silicon nitride (SiNx) nanomask layer over a GaN template, and (b) growing a thickness of a GaN film on top of the SiNx nanomask layer.
    Type: Grant
    Filed: May 9, 2007
    Date of Patent: May 25, 2010
    Assignee: The Regents of the University of California
    Inventors: Arpan Chakraborty, Kwang-Choong Kim, James S. Speck, Steven P. DenBaars, Umesh K. Mishra
  • Patent number: 7719020
    Abstract: An (Al, Ga, In)N and ZnO direct wafer bonded light emitting diode (LED), wherein light passes through electrically conductive ZnO. Flat and clean surfaces are prepared for both the (Al, Ga, In)N and ZnO wafers. A wafer bonding process is then performed between the (Al, Ga, In)N and ZnO wafers, wherein the (Al, Ga, In)N and ZnO wafers are joined together and then wafer bonded in a nitrogen ambient under uniaxial pressure at a set temperature for a set duration. After the wafer bonding process, ZnO is shaped for increasing light extraction from inside of LED.
    Type: Grant
    Filed: June 16, 2006
    Date of Patent: May 18, 2010
    Assignees: The Regents of the University of California, Japan Science and Technology Agency
    Inventors: Akihiko Murai, Christina Ye Chen, Daniel B. Thompson, Lee S. McCarthy, Steven P. DenBaars, Shuji Nakamura, Umesh K. Mishra
  • Publication number: 20100109018
    Abstract: A method for fabricating a single crystal, high quality, semi-insulating (SI) gallium nitride (GaN) layer using an AlxGa1-xN blocking layer. A buffer layer is grown on a substrate, the AlxGa1-xN blocking layer is grown on the buffer layer, and a single crystal, high quality, SI-GaN layer is grown on the AlxGa1-xN blocking layer. The AlxGa1-xN blocking layer acts as a diffusion blocking layer that prevents the diffusion of donors from the substrate from reaching the SI-GaN layer. The resulting SI-GaN layer reduces parasitic current flow and parasitic capacitive effects in electronic devices.
    Type: Application
    Filed: November 2, 2009
    Publication date: May 6, 2010
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Zhen Chen, Umesh K. Mishra, Steven P. DenBaars, Shuji Nakamura
  • Publication number: 20090246944
    Abstract: Methods for the heteroepitaxial growth of smooth, high quality films of N-face GaN film grown by MOCVD are disclosed. Use of a misoriented substrate and possibly nitridizing the substrate allow for the growth of smooth N-face GaN and other Group III nitride films as disclosed herein. The present invention also avoids the typical large (?m sized) hexagonal features which make N-face GaN material unacceptable for device applications. The present invention allows for the growth of smooth, high quality films which makes the development of N-face devices possible.
    Type: Application
    Filed: May 15, 2009
    Publication date: October 1, 2009
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Stacia Keller, Umesh K. Mishra, Nicholas K. Fichtenbaum
  • Publication number: 20090230411
    Abstract: The present invention discloses a plurality of interdigitated pixels arranged in an array, having a very low series-resistances with improved current spreading and improved heat-sinking. Each pixel is a square with sides of dimension l. The series resistance is minimized by increasing the perimeter of an active region for the pixels. The series resistance is also minimized by shrinking the space between a mesa and n-contact for each pixel.
    Type: Application
    Filed: April 7, 2009
    Publication date: September 17, 2009
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Arpan Chakraborty, Likun Shen, Umesh K. Mishra
  • Publication number: 20090218599
    Abstract: A method for fabricating a potential barrier for a nitrogen-face (N-face) nitride-based electronic device, comprising using a thickness and polarization induced electric field of a III-nitride interlayer, positioned between a first III-nitride layer and a second III-nitride layer, to shift, e.g., raise or lower, the first III-nitride layer's energy band with respect to the second III-nitride layer's energy band by a pre-determined amount. The first III-nitride layer and second III-nitride layer each have a higher or lower polarization coefficient than the III-nitride interlayer's polarization coefficient.
    Type: Application
    Filed: May 27, 2008
    Publication date: September 3, 2009
    Applicant: The Regents of the University of California
    Inventors: Umesh K. Mishra, Tomas A. Palacios Gutierrez, Man Hoi Wong
  • Patent number: 7525130
    Abstract: Novel GaN/AlGaN metal-semiconductor field-effect transistor (MESFET) structures grown without any impurity doping in the channel. A high-mobility polarization-induced bulk channel charge is created by grading the channel region linearly from GaN to Al0.3Ga0.7N over a distance, e.g., 1000 ?. A polarization-doped field effect transistor (PolFET) was fabricated and tested under DC and RF conditions. A current density of 850 mA/mm and transconductance of 93 mS/mm was observed under DC conditions. Small-signal characterization of 0.7 ?m gate length devices had a cutoff frequency, f?=19 GHz, and a maximum oscillation of fmax=46 GHz. The PolFETs perform better than comparable MESFETs with impurity-doped channels, and are suitable for high microwave power applications. An important advantage of these devices over AlGaN/GaN HEMTs is that the transconductance vs. gate voltage profile can be tailored by compositional grading for better large-signal linearity.
    Type: Grant
    Filed: September 29, 2005
    Date of Patent: April 28, 2009
    Assignee: The Regents of the University of California
    Inventors: Umesh K. Mishra, Huili Xing, Debdeep Jena, Siddharth Rajan
  • Patent number: 7518305
    Abstract: The present invention discloses a plurality of interdigitated pixels arranged in an array, having a very low series-resistances with improved current spreading and improved heat-sinking. Each pixel is a square with sides of dimension l. The series resistance is minimized by increasing the perimeter of an active region for the pixels. The series resistance is also minimized by shrinking the space between a mesa and n-contact for each pixel.
    Type: Grant
    Filed: November 1, 2005
    Date of Patent: April 14, 2009
    Assignee: The Regents of the University of California
    Inventors: Arpan Chakraborty, Likun Shen, Umesh K. Mishra
  • Publication number: 20090085065
    Abstract: A method for fabricating III-N semiconductor devices on the N-face of layers comprising (a) growing a III-nitride semiconductor device structure in a Ga-polar direction on a substrate, (b) attaching a Ga face of the III-nitride semiconductor device structure to a host substrate, and (c) removing the substrate to expose the N-face surface of the III-nitride semiconductor device structure. An N-polar (000-1) oriented III-nitride semiconductor device is also disclosed, comprising one or more (000-1) oriented nitride layers, each having an N-face opposite a group III-face, wherein at least one N-face is an at least partially exposed N-face, and a host substrate attached to one of the group III-faces.
    Type: Application
    Filed: March 31, 2008
    Publication date: April 2, 2009
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Umesh K. Mishra, Lee S. McCarthy, Chang Soo Suh, Siddharth Rajan
  • Patent number: 7504274
    Abstract: A method for the fabrication of nonpolar indium gallium nitride (InGaN) films as well as nonpolar InGaN-containing device structures using metalorganic chemical vapor deposition (MOVCD). The method is used to fabricate nonpolar InGaN/GaN violet and near-ultraviolet light emitting diodes and laser diodes.
    Type: Grant
    Filed: January 9, 2007
    Date of Patent: March 17, 2009
    Assignees: The Regents of the University of California, The Japan Science and Technology Agency
    Inventors: Arpan Chakraborty, Benjamin A. Haskell, Stacia Keller, James S. Speck, Steven P. DenBaars, Shuji Nakamura, Umesh K. Mishra
  • Publication number: 20080308813
    Abstract: High breakdown enhancement mode gallium nitride (GaN) based high electron mobility transistors (HEMTs) with integrated slant field plates. These HEMTs have an epilayer structure comprised of AlGaN/GaN buffer. Before the formation of the gate electrode, a passivation layer is deposited, and then the opening for the gate is patterned. The passivation layer below the gate is etched using an etch condition that creates a slanted sidewalls. Then, the charge below the channel is removed either by Fluorine-based plasma treatment and/or by a recess etch. The gate metal is deposited with an angled rotation to form a gate structure with an inherent field plate with rounded edges.
    Type: Application
    Filed: August 20, 2007
    Publication date: December 18, 2008
    Inventors: Chang Soo Suh, Yuvaraj Dora, Umesh K. Mishra
  • Publication number: 20080296618
    Abstract: An enhancement mode High Electron Mobility Transistor (HEMT) comprising a p-type nitride layer between the gate and a channel of the HEMT, for reducing an electron population under the gate. The HEMT may also comprise an Aluminum Nitride (AlN) layer between an AlGaN layer and buffer layer of the HEMT to reduce an on resistance of a channel.
    Type: Application
    Filed: June 2, 2008
    Publication date: December 4, 2008
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Chang Soo Suh, Umesh K. Mishra
  • Publication number: 20080296617
    Abstract: A method for fabricating an electronic device, comprising wafer bonding a first semiconductor material to a III-nitride semiconductor, at a temperature below 550° C., to form a device quality heterojunction between the first semiconductor material and the III-nitride semiconductor, wherein the first semiconductor material is different from the III-nitride semiconductor and is selected for superior properties, or preferred integration or fabrication characteristics in the injector region as compared to the III-nitride semiconductor.
    Type: Application
    Filed: May 1, 2008
    Publication date: December 4, 2008
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Umesh K. Mishra, Lee S. McCarthy
  • Publication number: 20080277682
    Abstract: A light emitting diode, comprising a substrate, a buffer layer on the substrate, an active layer on the buffer layer and between an n-type layer and a p-type layer, a tunnel junction adjacent the p-type layer, and n-type contacts to the tunnel junction and the n-type layer, wherein the buffer layer, n-type layer, p-type layer, active region and tunnel junction comprise III-nitride material grown in a nitrogen-face (N-face) orientation. The substrate surface upon which the III-nitride material is deposited is patterned to provide embedded backside roughening. A top surface of the tunnel junction, which also the top surface of the III-nitride material, is roughened.
    Type: Application
    Filed: March 31, 2008
    Publication date: November 13, 2008
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Umesh K. Mishra, Michael Grundmann, Steven P. DenBaars, Shuji Nakamura
  • Publication number: 20080258150
    Abstract: Structures to reduce dopant activation temperatures for ion implantation in III-N transistors, using low aluminum content layers in proximity to the conducting channel, are disclosed. A method to increase the temperature at which structures can be annealed by annealing in an active nitrogen ambient, for example, in NH3 in a metalorganic chemical vapor deposition (MOCVD) chamber, is also disclosed.
    Type: Application
    Filed: March 10, 2008
    Publication date: October 23, 2008
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Lee S. McCarthy, Umesh K. Mishra, Felix Recht, Tomas Apostol Palacios Gutierrez
  • Publication number: 20080237640
    Abstract: A method for fabricating nitrogen-face (N-face) nitride-based electronic devices with low buffer leakage, comprising isolating a buffer from a substrate with an AlGaInN nucleation layer to suppress impurity incorporation from the substrate into the buffer. A method for fabricating N-face nitride-based electronic devices with low parasitic resistance and high breakdown, comprising capping a device structure with a conductive layer to provide extremely low access and/or contact resistances, is also disclosed.
    Type: Application
    Filed: March 31, 2008
    Publication date: October 2, 2008
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Umesh K. Mishra, Yi Pei, Siddharth Rajan, Man Hoi Wong
  • Publication number: 20080116080
    Abstract: A gated electrode structure for altering a potential and electric field in an electrolyte near at least one working electrode is disclosed. The gated electrode structure may comprise a gate electrode biased appropriately with respect to a working electrode. Applying an appropriate static or dynamic (time varying) gate potential relative to the working electrode modifies the electric potential and field in an interfacial region between the working electrode and the electrolyte, and increases electron emission to and from states in the electrolyte, thereby facilitating an electrochemical, electrolytic or electrosynthetic reaction and reducing electrode overvoltage/overpotential.
    Type: Application
    Filed: November 20, 2007
    Publication date: May 22, 2008
    Applicant: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
    Inventors: Rakesh K. Lal, Likun Shen, Umesh K. Mishra