Patents by Inventor Isamu Akasaki

Isamu Akasaki 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: 20230369534
    Abstract: A semiconductor light emitting element includes: a growth substrate; a mask formed on the growth substrate; and a columnar semiconductor layer grown from at least one opening that is provided in the mask. The columnar semiconductor layer includes an n-type nanowire layer formed at a center thereof, an active layer formed on an outer periphery of the n-type nanowire layer, and a p-type semiconductor layer formed on an outer periphery of the active layer. An opening ratio of the opening is 0.1% or more and 5.0% or less, and a light emission wavelength is 480 nm or more.
    Type: Application
    Filed: August 25, 2021
    Publication date: November 16, 2023
    Applicants: KOITO MANUFACTURING CO., LTD., MEIJO UNIVERSITY
    Inventors: Satoshi KAMIYAMA, Tetsuya TAKEUCHI, Motoaki lWAYA, Isamu AKASAKI, Weifang LU, Kazuma ITO, Naoki SONE
  • Patent number: 11462659
    Abstract: Provided is a semiconductor light emitting device including a growth substrate; a pillar-shaped semiconductor layer formed on the growth substrate; and a buried semiconductor layer formed to cover the pillar-shaped semiconductor layer, wherein the pillar-shaped semiconductor layer has an n-type nanowire layer formed at a center, an active layer formed on an outermore side than the n-type nanowire layer, a p-type semiconductor layer formed on an outermore side than the active layer and a tunnel junction layer formed on an outermore side than the p-type semiconductor layer, and wherein at least a part of the pillar-shaped semiconductor layer is provided with a removed region formed by removing from the buried semiconductor layer to a part of the tunnel junction layer.
    Type: Grant
    Filed: September 9, 2020
    Date of Patent: October 4, 2022
    Assignees: KOITO MANUFACTURING CO., LTD., MEIJO UNIVERSITY, TOYODA GOSEI CO., LTD.
    Inventors: Satoshi Kamiyama, Tetsuya Takeuchi, Motoaki Iwaya, Isamu Akasaki, Lu Weifang, Naoki Sone, Kazuyoshi Iida, Ryo Nakamura, Masaki Oya
  • Publication number: 20220285580
    Abstract: The semiconductor light-emitting device includes an n-type semiconductor layer, a plurality of columnar semiconductors on the n-type semiconductor layer, a buried layer filling in a space between the columnar semiconductors, and a current suppression region suppressing a current. The columnar semiconductors has a hexagonal column and an active layer covering the hexagonal column. The hexagonal column has a hexagonal first surface and a second surface opposite to the first surface. The first surface of the columnar semiconductors faces the base layer. The second surface of the columnar semiconductors faces the current suppression region.
    Type: Application
    Filed: February 16, 2022
    Publication date: September 8, 2022
    Inventors: Koji Okuno, Koichi MUZUTANI, Masaki OYA, Kazuyoshi IIDA, Satoshi KAMIYAMA, Tetsuya TEKEUCHI, Motoaki IWAYA, Isamu AKASAKI
  • Publication number: 20220246793
    Abstract: To suppress current leakage between the semiconductor layer below the mask and the buried layer above the mask. To reduce the drive voltage and improve the emission efficiency by improving the efficiency of carrier injection into the active layer. The semiconductor light-emitting device includes a substrate, a mask, a columnar semiconductor, a buried layer, a cathode electrode, and an anode electrode. The substrate has a conductive substrate, an n-type semiconductor layer disposed on the conductive substrate, and a p-type semiconductor layer disposed on the n-type semiconductor layer. The p-type semiconductor layer has a high resistance, thereby enhancing insulation between the n-type semiconductor layer and the buried layer.
    Type: Application
    Filed: January 21, 2022
    Publication date: August 4, 2022
    Inventors: Koji OKUNO, Koichi MIZUTANI, Masaki OYA, Kazuyoshi IIDA, Satoshi KAMIYAMA, Tetsuya TAKEUCHI, Motoaki IWAYA, Isamu AKASAKI
  • Publication number: 20220246789
    Abstract: A buried layer forming step includes three steps of a facet structure forming step, a c-plane forming step, and a flattening step. In the facet structure forming step, a buried layer grows to form a periodic facet structure that matches an arrangement pattern of columnar semiconductors. In the c-plane forming step, the buried layer grows such that a {0001} plane (upper surface) is formed in a region of the buried layer corresponding to an upper portion of the columnar semiconductor. In the flattening step, lateral growth of the buried layer is promoted and the c-plane formed in the c-plane forming step is widened to flatten a surface of the buried layer.
    Type: Application
    Filed: January 28, 2022
    Publication date: August 4, 2022
    Inventors: Koji OKUNO, Koichi MIZUTANI, Masaki OYA, Kazuyoshi IIDA, Naoki SONE, Satoshi KAMIYAMA, Tetsuya TAKEUCHI, Motoaki IWAYA, Isamu AKASAKI
  • Patent number: 11146040
    Abstract: Included is a semiconductor multilayer film in which a non-doped InAlN layer and a GaN layer formed on said InAlN layer and containing a dopant are stacked a plurality of times.
    Type: Grant
    Filed: March 13, 2018
    Date of Patent: October 12, 2021
    Assignees: MEIJO UNIVERSITY, STANLEY ELECTRIC CO., LTD.
    Inventors: Tetsuya Takeuchi, Isamu Akasaki, Kazuki Kiyohara, Masaru Takizawa, Ji-Hao Liang
  • Publication number: 20210111538
    Abstract: Included is a semiconductor multilayer film in which a non-doped InAlN layer and a GaN layer formed on said InAlN layer and containing a dopant are stacked a plurality of times.
    Type: Application
    Filed: March 13, 2018
    Publication date: April 15, 2021
    Applicants: MEIJO UNIVERSITY, STANLEY ELECTRIC CO., LTD.
    Inventors: Tetsuya TAKEUCHI, Isamu AKASAKI, Kazuki KIYOHARA, Masaru TAKIZAWA, Ji-Hao LIANG
  • Publication number: 20210074877
    Abstract: Provided is a semiconductor light emitting device including a growth substrate; a pillar-shaped semiconductor layer formed on the growth substrate; and a buried semiconductor layer formed to cover the pillar-shaped semiconductor layer, wherein the pillar-shaped semiconductor layer has an n-type nanowire layer formed at a center, an active layer formed on an outermore side than the n-type nanowire layer, a p-type semiconductor layer formed on an outermore side than the active layer and a tunnel junction layer formed on an outermore side than the p-type semiconductor layer, and wherein at least a part of the pillar-shaped semiconductor layer is provided with a removed region formed by removing from the buried semiconductor layer to a part of the tunnel junction layer.
    Type: Application
    Filed: September 9, 2020
    Publication date: March 11, 2021
    Applicants: KOITO MANUFACTURING CO., LTD., MEIJO UNIVERSITY, TOYODA GOSEI CO., LTD.
    Inventors: Satoshi Kamiyama, Tetsuya Takeuchi, Motoaki Iwaya, Isamu Akasaki, Lu Weifang, Naoki Sone, Kazuyoshi Iida, Ryo Nakamura, Masaki Oya
  • Patent number: 10833223
    Abstract: To provide a Group III nitride semiconductor light-emitting device exhibiting the improved light extraction efficiency as well as reducing the influence of polarization that a p-type conductivity portion and an n-type conductivity portion occur in the AlGaN layer caused by the Al composition variation, and a production method therefor. A first p-type contact layer is a p-type AlGaN layer. A second p-type contact layer is a p-type AlGaN layer. The Al composition in the first p-type contact layer is reduced with distance from a light-emitting layer. The Al composition in the second p-type contact layer is reduced with distance from the light-emitting layer. The Al composition in the second p-type contact layer is lower than that in the first p-type contact layer. The Al composition variation rate to the unit thickness in the second p-type contact layer is higher than that in the first p-type contact layer.
    Type: Grant
    Filed: November 8, 2018
    Date of Patent: November 10, 2020
    Assignees: TOYODA GOSEI CO., LTD., MEIJO UNIVERSITY
    Inventors: Tetsuya Takeuchi, Satoshi Kamiyama, Motoaki Iwaya, Isamu Akasaki, Hisanori Kojima, Toshiki Yasuda, Kazuyoshi Iida
  • Publication number: 20200144451
    Abstract: Fabricating a high-quality nitride semiconductor crystal at a lower temperature. A nitride semiconductor crystal is fabricated by supplying onto a substrate (105) a group III element and/or a compound thereof, a nitrogen element and/or a compound thereof and an Sb element and/or a compound thereof, all of which serve as materials, and thereby vapor-growing at least one layer of nitride semiconductor film (104). A supply ratio of the Sb element to the nitrogen element in a growth process of the at least one layer of the nitride semiconductor film (104) is set to not less than 0.004.
    Type: Application
    Filed: January 9, 2020
    Publication date: May 7, 2020
    Applicant: MEIJO UNIVERSITY
    Inventors: Tetsuya TAKEUCHI, Tomoyuki SUZUKI, Hiroki SASAJIMA, Motoaki IWAYA, Isamu AKASAKI
  • Patent number: 10593831
    Abstract: Achieving resistance reduction of a nitride semiconductor multilayer film reflector. In the nitride semiconductor multilayer film reflector, a first semiconductor layer has a higher Al composition than a second semiconductor layer. A first composition-graded layer is interposed between the first and second semiconductor layers so as to be located at a group III element face side of the first semiconductor layer, the first composition-graded layer being adjusted so that its Al composition becomes lower as coming close to the second semiconductor layer. A second composition-graded layer is interposed between the first and second semiconductor layers so as to be located at a nitride face side of the first semiconductor layer. The second composition-graded layer is adjusted so that its Al composition becomes lower as coming close to the second semiconductor layer.
    Type: Grant
    Filed: March 19, 2014
    Date of Patent: March 17, 2020
    Assignee: MEIJO UNIVERSITY
    Inventors: Tetsuya Takeuchi, Motoaki Iwaya, Isamu Akasaki
  • Patent number: 10411438
    Abstract: Provided is a semiconductor multilayer film reflecting mirror formed by alternately repeating a first nitride film containing In (indium) and a second nitride film not containing In. The reflecting mirror includes an inter-film transition layer between the first and second nitride films, the composition of which is varied from the composition of the first nitride film to the composition of the second nitride film. The inter-film transition layer has a first transition layer formed on the first nitride film and containing In and Al (aluminum), and a second transition layer formed on the first transition layer and containing Al but not containing In. In the first transition layer, the percentages of In and Al are decreased from the first nitride film to the second transition layer, and the percentage of In in the first transition layer starts to decrease at a same or closer position to the first nitride film than the percentage of Al.
    Type: Grant
    Filed: December 8, 2017
    Date of Patent: September 10, 2019
    Assignees: STANLEY ELECTRIC CO., LTD., MEIJO UNIVERSITY
    Inventors: Tetsuya Takeuchi, Isamu Akasaki, Takanobu Akagi
  • Publication number: 20190148592
    Abstract: To provide a Group III nitride semiconductor light-emitting device exhibiting the improved light extraction efficiency as well as reducing the influence of polarization that a p-type conductivity portion and an n-type conductivity portion occur in the AlGaN layer caused by the Al composition variation, and a production method therefor. A first p-type contact layer is a p-type AlGaN layer. A second p-type contact layer is a p-type AlGaN layer. The Al composition in the first p-type contact layer is reduced with distance from a light-emitting layer. The Al composition in the second p-type contact layer is reduced with distance from the light-emitting layer. The Al composition in the second p-type contact layer is lower than that in the first p-type contact layer. The Al composition variation rate to the unit thickness in the second p-type contact layer is higher than that in the first p-type contact layer.
    Type: Application
    Filed: November 8, 2018
    Publication date: May 16, 2019
    Inventors: Tetsuya TAKEUCHI, Satoshi KAMIYAMA, Motoaki IWAYA, Isamu AKASAKI, Hisanori KOJIMA, Toshiki YASUDA, Kazuyoshi IIDA
  • Patent number: 10116120
    Abstract: A semiconductor multilayer film mirror is configured such that a pair of an InAlN-based semiconductor film and a GaN-based semiconductor film is layered a plurality of times in a cyclic fashion and the InAlN-based semiconductor film has an In composition of less than 18 at %. The semiconductor multilayer film mirror includes a thin GaN cap layer formed on the InAlN-based semiconductor film and an AlGaN layer formed on the thin GaN cap layer between each pair of the InAlN-based semiconductor film and the GaN-based semiconductor film.
    Type: Grant
    Filed: December 8, 2017
    Date of Patent: October 30, 2018
    Assignees: STANLEY ELECTRIC CO., LTD., MEIJO UNIVERSITY
    Inventors: Tetsuya Takeuchi, Isamu Akasaki, Shinichi Tanaka, Kazufumi Tanaka
  • Publication number: 20180166855
    Abstract: Provided is a semiconductor multilayer film reflecting mirror formed by alternately repeating a first nitride film containing In (indium) and a second nitride film not containing In. The reflecting mirror includes an inter-film transition layer between the first and second nitride films, the composition of which is varied from the composition of the first nitride film to the composition of the second nitride film. The inter-film transition layer has a first transition layer formed on the first nitride film and containing In and Al (aluminum), and a second transition layer formed on the first transition layer and containing Al but not containing In. In the first transition layer, the percentages of In and Al are decreased from the first nitride film to the second transition layer, and the percentage of In in the first transition layer starts to decrease at a same or closer position to the first nitride film than the percentage of Al.
    Type: Application
    Filed: December 8, 2017
    Publication date: June 14, 2018
    Applicants: MEIJO UNIVERSITY, STANLEY ELECTRIC CO., LTD.
    Inventors: Tetsuya TAKEUCHI, Isamu AKASAKI, Takanobu AKAGI
  • Publication number: 20180166856
    Abstract: A semiconductor multilayer film mirror is configured such that a pair of an InAlN-based semiconductor film and a GaN-based semiconductor film is layered a plurality of times in a cyclic fashion and the InAlN-based semiconductor film has an In composition of less than 18 at %. The semiconductor multilayer film mirror includes a thin GaN cap layer formed on the InAlN-based semiconductor film and an AlGaN layer formed on the thin GaN cap layer between each pair of the InAlN-based semiconductor film and the GaN-based semiconductor film.
    Type: Application
    Filed: December 8, 2017
    Publication date: June 14, 2018
    Applicants: MEIJO UNIVERSITY, STANLEY ELECTRIC CO., LTD.
    Inventors: Tetsuya TAKEUCHI, Isamu AKASAKI, Shinichi TANAKA, Kazufumi TANAKA
  • Patent number: 9847449
    Abstract: A nitride semiconductor light-emitting device with periodic gain active layers includes an n-type semiconductor layer, a p-type semiconductor layer and a resonator. The device further includes a plurality of active layers disposed between the n-type and p-type semiconductor layers so as to correspond to a peak intensity position of light existing in the resonator and at least one interlayer disposed between the active layers. The active layer disposed at the p-type semiconductor layer side has a larger light emission intensity than the active layer disposed at the n-type semiconductor layer side.
    Type: Grant
    Filed: December 1, 2015
    Date of Patent: December 19, 2017
    Assignees: MEIJO UNIVERSITY, STANLEY ELECTRIC CO., LTD.
    Inventors: Kenjo Matsui, Tetsuya Takeuchi, Motoaki Iwaya, Isamu Akasaki, Takanobu Akagi, Sho Iwayama
  • Patent number: 9716209
    Abstract: This application provides a method of manufacturing an n-p-n nitride-semiconductor light-emitting device which includes a current confinement region (A) using a buried tunnel junction layer and in which a favorable luminous efficacy can be obtained and to provide the n-p-n nitride-semiconductor light-emitting device. The p-type activation of a p-type GaN crystal layer stacked below a tunnel junction layer is performed in an intermediate phase of a manufacturing process in which the p-type GaN crystal layer is exposed to atmosphere gas with the tunnel junction layer partially removed, before the tunnel junction layer is buried in an n-type GaN crystal layer. In the intermediate phase of the manufacturing process in which the p-type GaN crystal layer is exposed, p-type activation is efficiently performed on the p-type GaN crystal layer, and a p-type GaN crystal layer with low electric resistance can be obtained.
    Type: Grant
    Filed: August 23, 2016
    Date of Patent: July 25, 2017
    Assignee: MELIO UNIVERSITY
    Inventors: Tetsuya Takeuchi, Yuka Kuwano, Motoaki Iwaya, Isamu Akasaki
  • Publication number: 20170155016
    Abstract: Fabricating a high-quality nitride semiconductor crystal at a lower temperature. A nitride semiconductor crystal is fabricated by supplying onto a substrate (105) a group III element and/or a compound thereof, a nitrogen element and/or a compound thereof and an Sb element and/or a compound thereof, all of which serve as materials, and thereby vapor-growing at least one layer of nitride semiconductor film (104). A supply ratio of the Sb element to the nitrogen element in a growth process of the at least one layer of the nitride semiconductor film (104) is set to not less than 0.004.
    Type: Application
    Filed: March 4, 2014
    Publication date: June 1, 2017
    Applicant: MEIJO UNIVERSITY
    Inventors: Tetsuya TAKEUCHI, Tomoyuki SUZUKI, Hiroki SASAJIMA, Motoaki IWAYA, Isamu AKASAKI
  • Patent number: 9666753
    Abstract: A nitride semiconductor light emitting device includes a substrate as a base and an n-type semiconductor layer grown on a surface side of the substrate. Antimony (Sb) is added to the n-type semiconductor layer so that a molar fraction is not less than 0.1% and is less than 1%. A concentration of an n-type impurity in the n-type semiconductor layer is lower than an electron concentration.
    Type: Grant
    Filed: April 8, 2016
    Date of Patent: May 30, 2017
    Assignee: MEIJO UNIVERSITY
    Inventors: Tetsuya Takeuchi, Daisuke Komori, Kaku Takarabe, Motoaki Iwaya, Isamu Akasaki