Patents by Inventor Yoshitaka Kuraoka

Yoshitaka Kuraoka 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: 20230250555
    Abstract: It is provided a method of growing a group 13 nitride crystal layer, on an underlying substrate including a seed crystal layer composed of a group 13 nitride. The underlying substrate is immersed in a melt containing a flux to grow a group 13 nitride crystal layer two-dimensionally on a nitrogen polar surface of the seed crystal layer by flux method.
    Type: Application
    Filed: April 14, 2023
    Publication date: August 10, 2023
    Inventors: Yoshitaka KURAOKA, Kentaro NONAKA
  • Publication number: 20230215969
    Abstract: It is provided a seed crystal layer, composed of a group 13 nitride crystal selected from gallium nitride, aluminum nitride, indium nitride or the mixed crystals thereof, on an alumina layer on a single crystal substrate. By annealing under reducing atmosphere at a temperature of 950° C. or higher and 1200° C. or lower, convex-concave morphology is formed on a surface of the seed crystal layer so as to have an RMS value of 180 nm to 700 nm measured by an atomic force microscope. On the surface of the seed crystal layer, it is grown a group 13 nitride crystal layer composed of a group 13 nitride crystal selected from gallium nitride, aluminum nitride, indium nitride or the mixed crystals thereof.
    Type: Application
    Filed: March 10, 2022
    Publication date: July 6, 2023
    Inventors: Masahiro SAKAI, Takayuki HIRAO, Hirokazu NAKANISHI, Mikiya ICHIMURA, Takanao SHIMODAIRA, Takashi YOSHINO, Katsuhiro IMAI, Yoshitaka KURAOKA
  • Publication number: 20220209062
    Abstract: Provided are a light emitting device having a support layer having a surface with a three-dimensional shape, a light emitting functional layer formed on the surface with a three-dimensional shape of the support layer, and a translucent electrode layer provided on a side of the light emitting functional layer opposite to the support layer. The support layer functions as a reflective electrode, and a light emitting functional layer formed on the surface with a three-dimensional shape of the support layer. The light emitting functional layer has two or more layers composed of semiconductor single crystal grains. Each of the two or more layers has a single crystal structure in a direction approximately normal to the surface with a three-dimensional shape.
    Type: Application
    Filed: March 21, 2022
    Publication date: June 30, 2022
    Applicant: NGK INSULATORS, LTD.
    Inventors: Masahiko Namerikawa, Takashi Yoshino, Yoshitaka Kuraoka, Masahiro Sakai
  • Publication number: 20220199854
    Abstract: It is provided a seed crystal layer, composed of a group 13 nitride crystal selected from gallium nitride, aluminum nitride, indium nitride or the mixed crystals thereof, on an alumina layer on a single crystal substrate. By annealing under reducing atmosphere at a temperature of 950° C. or higher and 1200° C. or lower, convex-concave morphology is formed on a surface of the seed crystal layer so as to have an RMS value of 180 nm to 700 nm measured by an atomic force microscope. On the surface of the seed crystal layer, it is grown a group 13 nitride crystal layer composed of a group 13 nitride crystal selected from gallium nitride, aluminum nitride, indium nitride or the mixed crystals thereof.
    Type: Application
    Filed: March 10, 2022
    Publication date: June 23, 2022
    Inventors: Masahiro SAKAI, Takayuki HIRAO, Hirokazu NAKANISHI, Mikiya ICHIMURA, Takanao SHIMODAIRA, Takashi YOSHINO, Katsuhiro IMAI, Yoshitaka KURAOKA
  • Publication number: 20210013366
    Abstract: A group 13 nitride layer is composed of a polycrystalline group 13 nitride and is constituted by a plurality of monocrystalline particles having a particular crystal orientation approximately in a normal direction. The group 13 nitride comprises gallium nitride, aluminum nitride, indium nitride or the mixed crystal thereof. The group 13 nitride layer includes an upper surface and a bottom surface, and a full width at half maximum of a (1000) plane reflection of X-ray rocking curve on the upper surface is 20000 seconds or less and 1500 seconds or more.
    Type: Application
    Filed: September 28, 2020
    Publication date: January 14, 2021
    Inventors: Masahiro SAKAI, Takashi YOSHINO, Katsuhiro IMAI, Yoshitaka KURAOKA
  • Patent number: 10804432
    Abstract: A free-standing substrate of a polycrystalline nitride of a group 13 element contains a plurality of monocrystalline particles having a particular crystal orientation in approximately a normal direction. The polycrystalline nitride of the group 13 element is composed of gallium nitride, aluminum nitride, indium nitride or a mixed crystal thereof. The free-standing substrate has a top surface and bottom surface. The free-standing substrate contains at least one of zinc and calcium. A root mean square roughness Rms at the top surface is 3.0 nm or less.
    Type: Grant
    Filed: August 9, 2018
    Date of Patent: October 13, 2020
    Assignee: NGK INSULATORS, LTD.
    Inventors: Katsuhiro Imai, Yoshitaka Kuraoka, Mikiya Ichimura, Takayuki Hirao
  • Patent number: 10770552
    Abstract: An epitaxial substrate for semiconductor elements suppresses leakage current and has a high breakdown voltage. The epitaxial substrate for semiconductor elements includes: a semi-insulating free-standing substrate formed of GaN doped with Zn; a buffer layer formed of a group 13 nitride adjacent to the free-standing substrate; a channel layer formed of a group 13 nitride adjacent to the buffer layer; and a barrier layer formed of a group 13 nitride on an opposite side of the buffer layer with the channel layer therebetween, wherein part of a first region consisting of the free-standing substrate and the buffer layer is a second region containing Si at a concentration of 1×1017cm?3 or more, and a minimum value of a concentration of Zn in the second region is 1×1017cm?3.
    Type: Grant
    Filed: January 3, 2020
    Date of Patent: September 8, 2020
    Assignee: NGK INSULATORS, LTD.
    Inventors: Mikiya Ichimura, Sota Maehara, Yoshitaka Kuraoka
  • Patent number: 10734548
    Abstract: A free-standing substrate of a polycrystalline nitride of a group 13 element is composed of a plurality of monocrystalline particles having a particular crystal orientation in approximately a normal direction. The free-standing substrate has a top surface and a bottom surface. The polycrystalline nitride of the group 13 element is gallium nitride, aluminum nitride, indium nitride or a mixed crystal thereof and contains zinc at a concentration of 1×1017 atoms/cm3 or more and 1×1020 atoms/cm3 or less.
    Type: Grant
    Filed: August 9, 2018
    Date of Patent: August 4, 2020
    Assignee: NGK INSULATORS, LTD.
    Inventors: Katsuhiro Imai, Yoshitaka Kuraoka, Mikiya Ichimura, Takayuki Hirao
  • Patent number: 10707373
    Abstract: There is provided a self-supporting polycrystalline gallium nitride substrate having excellent characteristics such as high luminous efficiency and high conversion efficiency when used for devices, such as light emitting devices and solar cells. The self-supporting polycrystalline gallium nitride substrate is composed of gallium nitride-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate, and has a top surface and a bottom surface. The crystal orientations of individual gallium nitride-based single crystal grains as determined from inverse pole figure mapping by electron backscatter diffraction (EBSD) analysis on the top surface are distributed at various tilt angles from the specific crystal orientation, in which the average tilt angle thereof is 0.1° or more and less than 1° and the cross-sectional average diameter DT of the gallium nitride-based single crystal grains at the outermost surface exposed on the top surface is 10 ?m or more.
    Type: Grant
    Filed: August 9, 2018
    Date of Patent: July 7, 2020
    Assignee: NGK Insulators, Ltd.
    Inventors: Morimichi Watanabe, Kei Sato, Yoshitaka Kuraoka, Katsuhiro Imai, Tsutomu Nanataki
  • Publication number: 20200144373
    Abstract: An epitaxial substrate for semiconductor elements suppresses leakage current and has a high breakdown voltage. The epitaxial substrate for semiconductor elements includes: a semi-insulating free-standing substrate formed of GaN doped with Zn; a buffer layer formed of a group 13 nitride adjacent to the free-standing substrate; a channel layer formed of a group 13 nitride adjacent to the buffer layer; and a barrier layer formed of a group 13 nitride on an opposite side of the buffer layer with the channel layer therebetween, wherein part of a first region consisting of the free-standing substrate and the buffer layer is a second region containing Si at a concentration of 1×1017cm?3 or more, and a minimum value of a concentration of Zn in the second region is 1×1017cm?3.
    Type: Application
    Filed: January 3, 2020
    Publication date: May 7, 2020
    Inventors: Mikiya ICHIMURA, Sota MAEHARA, Yoshitaka KURAOKA
  • Patent number: 10629688
    Abstract: An epitaxial substrate for semiconductor elements suppresses leakage current and has a high breakdown voltage. The epitaxial substrate for semiconductor elements includes: a semi-insulating free-standing substrate formed of GaN doped with Zn; a buffer layer formed of a group 13 nitride adjacent to the free-standing substrate; a channel layer formed of a group 13 nitride adjacent to the buffer layer; and a barrier layer formed of a group 13 nitride on an opposite side of the buffer layer with the channel layer therebetween, wherein part of a first region consisting of the free-standing substrate and the buffer layer is a second region containing Si at a concentration of 1×1017 cm?3 or more, and a minimum value of a concentration of Zn in the second region is 1×1017 cm?3.
    Type: Grant
    Filed: April 25, 2018
    Date of Patent: April 21, 2020
    Assignee: NGK INSULATORS, LTD.
    Inventors: Mikiya Ichimura, Sota Maehara, Yoshitaka Kuraoka
  • Patent number: 10598369
    Abstract: A heat discharge structure that includes a film of a nitride of a group 13 element having a first main face, a second main face and an outer side end face. The structure further includes a portion for containing the light source device. The portion has a through hole opening at the first main face and the second main face, and a fixing face for fixing the light source device. The fixing face faces the through hole and contacts the light source device.
    Type: Grant
    Filed: June 18, 2018
    Date of Patent: March 24, 2020
    Assignee: NGK INSULATORS, LTD.
    Inventors: Masahiko Namerikawa, Takashi Yoshino, Katsuhiro Imai, Yoshitaka Kuraoka
  • Patent number: 10580646
    Abstract: An epitaxial substrate for semiconductor elements is provided which suppresses the occurrence of current collapse. The epitaxial substrate for the semiconductor elements includes: a semi-insulating free-standing substrate formed of GaN doped with Zn; a buffer layer adjacent to the free-standing substrate; a channel layer adjacent to the buffer layer; and a barrier layer provided on an opposite side of the buffer layer with the channel layer therebetween, wherein the buffer layer is a diffusion suppressing layer formed of AlpGa1-pN (0.7?p?1) and suppresses diffusion of Zn from the free-standing substrate into the channel layer.
    Type: Grant
    Filed: April 27, 2018
    Date of Patent: March 3, 2020
    Assignee: NGK INSULATORS, LTD.
    Inventors: Mikiya Ichimura, Sota Maehara, Yoshitaka Kuraoka
  • Patent number: 10541514
    Abstract: A vertical external-cavity surface-emitting laser (VECSEL) whose blueshift is reduced also in a high intensity range of emitted laser light is realized. A surface-emitting device for VECSEL includes a base substrate made of GaN and c-axis oriented, and an emitter structure formed of a group 13 nitride semiconductor and provided on the base substrate. The emitter structure is formed of unit deposition parts, each of which is provided on the base substrate and includes a DBR layer having a distributed Bragg reflection structure and an active layer that has a multiple quantum well structure and generates excitation emission in response to irradiation with external laser light. A c-axis orientation of each of the unit deposition parts conforms to the c-axis orientation of the base substrate located directly below the unit deposition parts. Grooves are formed between the unit deposition parts.
    Type: Grant
    Filed: February 9, 2017
    Date of Patent: January 21, 2020
    Assignee: NGK INSULATORS, LTD.
    Inventors: Yoshitaka Kuraoka, Kentaro Nonaka, Tomohiko Sugiyama, Takashi Yoshino
  • Patent number: 10418239
    Abstract: Provided is an epitaxial substrate for semiconductor elements which suppresses an occurrence of current collapse. The epitaxial substrate for the semiconductor elements includes: a semi-insulating free-standing substrate formed of GaN being doped with Zn; a buffer layer being adjacent to the free-standing substrate; a channel layer being adjacent to the buffer layer; and a barrier layer being provided on an opposite side of the buffer layer with the channel layer therebetween, wherein the buffer layer is a diffusion suppressing layer formed of Al-doped GaN and suppresses diffusion of Zn from the free-standing substrate into the channel layer.
    Type: Grant
    Filed: April 27, 2018
    Date of Patent: September 17, 2019
    Assignee: NGK INSULATORS, LTD.
    Inventors: Mikiya Ichimura, Sota Maehara, Yoshitaka Kuraoka
  • Patent number: 10410859
    Abstract: An epitaxial substrate for semiconductor elements which suppresses the occurrence of current collapse. The epitaxial substrate for the semiconductor elements includes: a semi-insulating free-standing substrate formed of GaN doped with Zn; a buffer layer adjacent to the free-standing substrate; a channel layer adjacent to the buffer layer; and a barrier layer provided on an opposite side of the buffer layer with the channel layer provided therebetween, wherein the buffer layer is a diffusion suppressing layer that suppresses the diffusion of Zn from the free-standing substrate into the channel layer.
    Type: Grant
    Filed: April 27, 2018
    Date of Patent: September 10, 2019
    Assignee: NGK INSULATORS, LTD.
    Inventors: Mikiya Ichimura, Sota Maehara, Yoshitaka Kuraoka
  • Patent number: 10347755
    Abstract: Provided are a group 13 nitride composite substrate allowing for the production of a semiconductor device suitable for high-frequency applications while including a conductive GaN substrate, and a semiconductor device produced using this substrate. The group 13 nitride composite substrate includes a base material of an n-conductivity type formed of GaN, a base layer located on the base material, being a group 13 nitride layer having a resistivity of 1×106 ?·cm or more, a channel layer located on the base layer, being a GaN layer having a total impurity density of 1×1017/cm3 or less, and a barrier layer that is located on the channel layer and is formed of a group 13 nitride having a composition AlxInyGa1-x-yN (0?x?1, 0?y?1).
    Type: Grant
    Filed: November 18, 2016
    Date of Patent: July 9, 2019
    Assignee: NGK INSULATORS, LTD.
    Inventors: Yoshitaka Kuraoka, Mikiya Ichimura, Makoto Iwai
  • Patent number: 10332975
    Abstract: Provided is a group 13 nitride epitaxial substrate with which the HEMT device having superior characteristics can be manufactured. This epitaxial substrate is provided with: a base substrate composed of SiC and having a main surface with a (0001) plane orientation; a nucleation layer formed on one main surface of the base substrate and composed of AlN; an electron transit layer formed on the nucleation layer and composed of a group 13 nitride with the composition AlyGa1-yN (0?y<1); and a barrier layer formed on the electron transit layer and composed of a group 13 nitride with the composition InzAl1-zN (0.13?z?0.23) or AlwGa1-wN (0.15?w?0.35). The (0001) plane of the base substrate has an off angle of 0.1° or more and 0.5° or less, and an intermediate layer composed of a group 13 nitride with the composition AlxGa1-xN (0.01 ?x?0.4) is further provided between the nucleation layer and the electron transit layer.
    Type: Grant
    Filed: March 24, 2017
    Date of Patent: June 25, 2019
    Assignee: NGK INSULATORS, LTD.
    Inventors: Mikiya Ichimura, Sota Maehara, Yoshitaka Kuraoka
  • Publication number: 20190027359
    Abstract: Provided is an epitaxial substrate for semiconductor elements which suppresses an occurrence of current collapse. The epitaxial substrate for the semiconductor elements includes: a semi-insulating free-standing substrate formed of GaN being doped with Zn; a buffer layer being adjacent to the free-standing substrate; a channel layer being adjacent to the buffer layer; and a barrier layer being provided on an opposite side of the buffer layer with the channel layer therebetween, wherein the buffer layer is a diffusion suppressing layer that suppresses diffusion of Zn from the free-standing substrate into the channel layer.
    Type: Application
    Filed: April 27, 2018
    Publication date: January 24, 2019
    Inventors: Mikiya ICHIMURA, Sota MAEHARA, Yoshitaka KURAOKA
  • Publication number: 20180351038
    Abstract: There is provided a self-supporting polycrystalline gallium nitride substrate having excellent characteristics such as high luminous efficiency and high conversion efficiency when used for devices, such as light emitting devices and solar cells. The self-supporting polycrystalline gallium nitride substrate is composed of gallium nitride-based single crystal grains having a specific crystal orientation in a direction approximately normal to the substrate, and has a top surface and a bottom surface. The crystal orientations of individual gallium nitride-based single crystal grains as determined from inverse pole figure mapping by electron backscatter diffraction (EBSD) analysis on the top surface are distributed at various tilt angles from the specific crystal orientation, in which the average tilt angle thereof is 0.1° or more and less than 1° and the cross-sectional average diameter DT of the gallium nitride-based single crystal grains at the outermost surface exposed on the top surface is 10 ?m or more.
    Type: Application
    Filed: August 9, 2018
    Publication date: December 6, 2018
    Applicant: NGK INSULATORS, LTD.
    Inventors: Morimichi WATANABE, Kei Sato, Yoshitaka Kuraoka, Katsuhiro Imai, Tsutomu Nanataki