Patents by Inventor Tetsuya Akasaka

Tetsuya Akasaka 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: 20210272794
    Abstract: First, in a first step, a semiconductor layer that is constituted by a nitride semiconductor and includes a group V polar surface as a main surface is formed. Next, in a second step, nitrogen atoms at the surface of the semiconductor layer are substituted with a group VI element that is any of oxygen, sulfur, selenium, and tellurium. Next, in a third step, a layered material layer is formed through epitaxial growth of a layered material on the semiconductor layer at which nitrogen atoms are substituted with the group VI element.
    Type: Application
    Filed: June 28, 2019
    Publication date: September 2, 2021
    Inventors: Koji Onomitsu, Tetsuya Akasaka, Masanobu Hiroki, Junichi Nishinaka, Kazuhide Kumakura
  • Patent number: 9219111
    Abstract: A nitride semiconductor structure of the present invention is obtained by growing an h- or t-BN thin film (12) and a wurtzite-structure AlxGa1-xN (x>0) thin film (14) as buffer layers and forming a single-crystal wurtzite-structure AlGaInBN thin film (13) thereon. While GaN, AlGaN, AlN, and the like have the wurtzite structure with sp3 bonds, h-BN or t-BN has the graphite structure with sp2 bonds, and has a completely different crystal structure. Accordingly, it has heretofore not been considered that a wurtzite-structure AlGaInBN thin film can be grown on a graphite-structure h-BN thin film. However, when a wurtzite-structure AlxGa1-xN (x>0) thin film (14) is formed as a buffer layer on a graphite-structure boron nitride thin film (12), a wurtzite-structure AlGaInBN (13) nitride semiconductor structure such as GaN can be grown on the buffer layer.
    Type: Grant
    Filed: September 5, 2012
    Date of Patent: December 22, 2015
    Assignee: Nippon Telegraph and Telephone Corporation
    Inventors: Yasuyuki Kobayashi, Kazuhide Kumakura, Tetsuya Akasaka, Toshiki Makimoto
  • Publication number: 20140145147
    Abstract: A nitride semiconductor structure of the present invention is obtained by growing an h- or t-BN thin film (12) and a wurtzite-structure AlxGa1-xN (x>0) thin film (14) as buffer layers and forming a single-crystal wurtzite-structure AlGaInBN thin film (13) thereon. While GaN, AlGaN, AlN, and the like have the wurtzite structure with sp3 bonds, h-BN or t-BN has the graphite structure with sp2 bonds, and has a completely different crystal structure. Accordingly, it has heretofore not been considered that a wurtzite-structure AlGaInBN thin film can be grown on a graphite-structure h-BN thin film. However, when a wurtzite-structure AlxGa1-xN (x>0) thin film (14) is formed as a buffer layer on a graphite-structure boron nitride thin film (12), a wurtzite-structure AlGaInBN (13) nitride semiconductor structure such as GaN can be grown on the buffer layer.
    Type: Application
    Filed: September 5, 2012
    Publication date: May 29, 2014
    Inventors: Yasuyuki Kobayashi, Kazuhide Kumakura, Tetsuya Akasaka, Toshiki Makimoto
  • Patent number: 6920166
    Abstract: A masking material 13, which includes stripe-like openings 12 parallel to the [1-100] direction of a nitride semiconductor thin film, is formed on a substrate. Nitride semiconductor thin films 11 doped with Mg are grown on the openings 12 by selective-area growth. The nitride semiconductor thin films 11 are composed of a portion 14 formed as a result of the growth in the direction perpendicular to a (0001) principal plane, and a portion 15 formed as a result of the growth of {11-2x} facets (x=0, 1, 2). The Mg concentration of the portion 15 is made lower than that of the portion 14.
    Type: Grant
    Filed: March 17, 2003
    Date of Patent: July 19, 2005
    Assignee: Nippon Telegraph & Telephone Corporation
    Inventors: Tetsuya Akasaka, Seigo Ando, Toshio Nishida, Naoki Kobayashi, Tadashi Saitoh
  • Publication number: 20030179793
    Abstract: A masking material 13, which includes stripe-like openings 12 parallel to the [1-100] direction of a nitride semiconductor thin film, is formed on a substrate. Nitride semiconductor thin films 11 doped with Mg are grown on the openings 12 by selective-area growth. The nitride semiconductor thin films 11 are composed of a portion 14 formed as a result of the growth in the direction perpendicular to a (0001) principal plane, and a portion 15 formed as a result of the growth of {11-2x} facets (x=0, 1, 2). The Mg concentration of the portion 15 is made lower than that of the portion 14.
    Type: Application
    Filed: March 17, 2003
    Publication date: September 25, 2003
    Applicant: Nippon Telegraph and Telephone Corporation
    Inventors: Tetsuya Akasaka, Seigo Ando, Toshio Nishida, Naoki Kobayashi, Tadashi Saitoh