Patents by Inventor Ken Nakahara

Ken Nakahara 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: 20110114938
    Abstract: Provided is a ZnO-based semiconductor device in which, in the case of forming a laminate including an acceptor-doped layer made of a ZnO-based semiconductor, the properties of a film can be stabilized by preventing deterioration of the flatness of the acceptor-doped layer or a layer after the acceptor-doped layer and an increase of crystal defect in the layer, without lowering the concentration of an acceptor element.
    Type: Application
    Filed: February 20, 2009
    Publication date: May 19, 2011
    Applicant: Rohm Co., Ltd.
    Inventors: Ken Nakahara, Kentaro Tamura, Hiroyuki Yuji, Shunsuke Akasaka, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Patent number: 7906791
    Abstract: Light extraction efficiency of a semiconductor light-emitting element is improved. A buffer layer, an n-type GaN layer, an InGaN emission layer, and a p-type GaN layer are laminated on a sapphire substrate in a semiconductor light-emitting element. A ZnO layer functioning as a transparent electrode is provided on the p-type GaN layer and concave portions are formed on a surface of the ZnO layer at two-dimensional periodic intervals. If a wavelength of light from the InGaN emission layer in the air is ?, an index of refraction of the ZnO layer at the wavelength ? is nz?, and a total reflection angle at an interface between the ZnO layer and a medium in contact therewith is ?z, a periodic interval Lz between adjacent concave portions is set in a range of ?/nz??Lz??/(nz?×(1?sin ?z)).
    Type: Grant
    Filed: March 3, 2006
    Date of Patent: March 15, 2011
    Assignee: Rohm Co., Ltd.
    Inventor: Ken Nakahara
  • Publication number: 20110037067
    Abstract: Provided is a ZnO-based semiconductor device in which flat ZnO-based semiconductor layers can be grown on a MgZnO substrate having a laminate-side principal surface including a C-plane. With an MgxZn1-xO substrate (0?x<1) with a principal surface including a C-plane, the principal surface is formed so that an angle ?m made between a c-axis of substrate's crystal axes and a projection axis obtained by projecting a normal line to the principal surface onto a plane defined by an m-axis and the c-axis of the substrate's crystal axes can be within a range of 0<?m?3. On the principal surface thus formed, ZnO-based semiconductor layers 2 to 5 are grown epitaxially. A p electrode 8 is formed on the ZnO-based semiconductor layer 5, and an n electrode 9 is formed on the bottom side of the MgxZn1-xO substrate 1. In this way, steps are formed on the surface of the MgxZn1-xO substrate 1, while being arranged regularly in the m-axis direction.
    Type: Application
    Filed: November 20, 2008
    Publication date: February 17, 2011
    Inventors: Ken Nakahara, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Publication number: 20110033718
    Abstract: Provided is a ZnO-based thin film which is doped with p-type impurities and which can be used for various devices. An MgxZn1-xO film (0?x?0.5) is formed on top of a substrate so as to have an acceptor concentration of a p-type dopant that is 5×1020 cm?3 or less. An acceptor concentration exceeding 5×1020 cm?3 results in the formation of a mixed crystal of the p-type impurities and the ZnO crystal as the base material. Accordingly, no high-quality ZnO-based thin film doped to be p-type can be obtained. This fact is testified by the change observed in the ZnO secondary ion intensity.
    Type: Application
    Filed: April 2, 2008
    Publication date: February 10, 2011
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Hiroyuki Yuji, Kentaro Tamura, Shunsuke Akasaka, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Patent number: 7872269
    Abstract: Provided is a gallium nitride semiconductor light emitting element capable of stabilizing a drive voltage by reducing carrier depletion attributable to spontaneous polarization and piezo polarization generated at the interface between an AlGaN semiconductor layer and a GaN semiconductor layer. A gallium nitride semiconductor crystal 2 including a light emitting region is formed on the R plane of a sapphire substrate 1. In addition, in another constitution, a gallium nitride semiconductor crystal 2 is formed on the A plane of a GaN substrate 3 or on the M plane of a GaN substrate 4. The growth surface of these gallium nitride semiconductor crystals 2 are not an N (nitrogen) polar face or a Ga polar face but are non-polar faces. This can decrease the strength of an electric field caused by spontaneous polarization and piezo polarization generated at the interface of GaN/AlGaN at the p side. Thus, carrier depletion can be avoided.
    Type: Grant
    Filed: November 29, 2006
    Date of Patent: January 18, 2011
    Assignee: ROHM Co., Ltd.
    Inventor: Ken Nakahara
  • Publication number: 20100323160
    Abstract: Provided is a ZnO-based thin film for growing a flat film when the ZnO-based thin film is formed on a substrate. In FIG. 1(a), a ZnO-based film 2 is formed on a ZnO-based substrate 1. Meanwhile, in FIG. 1(b), a ZnO-based laminated body 10 that is a laminated body of ZnO-based thin films is formed on the ZnO-based substrate 1. The ZnO-based laminated body 10 is the laminated body in which multiple ZnO-based thin films including a ZnO-based thin film 3, a ZnO-based thin film 4 and the like are laminated. When forming the ZnO-based thin film 2 or the ZnO-based laminated body 10, the film or the body is formed at a growth temperature of 750° C. or above, or alternatively, a step structure on a surface of the film is formed into a predetermined structure such that roughness on the surface of the film is in a predetermined range.
    Type: Application
    Filed: February 6, 2008
    Publication date: December 23, 2010
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Hiroyuki Yuji, Kentaro Tamura, Shunsuke Akasaka, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Publication number: 20100308327
    Abstract: Provided are a ZnO-based substrate having a high-quality surface suitable for crystal growth, a method for processing the ZnO-based substrate, and a ZnO-based semiconductor device. The ZnO-based substrate is formed such that any one of a carboxyl group and a carbonate group is substantially absent in a principal surface on a crystal growth side. Also, in order for a carboxyl group or a carbonate group to be substantially absent, any one of oxygen radicals, oxygen plasma and ozone is brought into contact with the surface of the ZnO-based substrate before the crystal growth is started. Consequently, cleanness of the surface of the ZnO substrate is enhanced, thereby enabling fabrication of a high-quality ZnO-based thin film on the substrate.
    Type: Application
    Filed: January 30, 2009
    Publication date: December 9, 2010
    Inventors: Ken Nakahara, Shunsuke Akasaka, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Publication number: 20100289004
    Abstract: Provided are a ZnO-based thin film and a ZnO-based semiconductor device which allow: reduction in a burden on a manufacturing apparatus; improvement of controllability and reproducibility of doping; and obtaining p-type conduction without changing a crystalline structure. In order to be formed into a p-type ZnO-based thin film, a ZnO-based thin film is formed by employing as a basic structure a superlattice structure of a MgZnO/ZnO super lattice layer 3. This superlattice component is formed with a laminated structure which includes acceptor-doped MgZnO layers 3b and acceptor-doped ZnO layers 3a. Hence, it is possible to improve controllability and reproducibility of the doping, and to prevent a change in a crystalline structure due to a doping material.
    Type: Application
    Filed: June 13, 2008
    Publication date: November 18, 2010
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Shunsuke Akasaka, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Publication number: 20100270533
    Abstract: Provided is a ZnO-based semiconductor device capable of achieving easier conversion into p-type by alleviating the self-compensation effect and by preventing donor impurities from mixing in. The ZnO-based semiconductor device includes a MgxZn1-xO substrate (0?x?1) having such a principal surface that: a projection axis obtained by projecting a normal line to the principal surface onto a plane formed by an a-axis and a c-axis of substrate crystal axes is inclined towards the a-axis by an angle of ?a degrees; a projection axis obtained by projecting the normal line to the principal surface onto a plane formed by an m-axis and the c-axis of the substrate crystal axes is inclined towards the m-axis by an angle of ?m degrees; the angle ?a satisfies 70?{90?(180/?)arctan(tan(??a/180)/tan(??m/180))?110; and the angle ?m?1.
    Type: Application
    Filed: September 5, 2008
    Publication date: October 28, 2010
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Hiroyuki Yuji, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Publication number: 20100237343
    Abstract: Provided are a ZnO-based thin film which is inhibited from being doped with an unintentional impurity, and a semiconductor device. The ZnO-based thin film has a main surface: which is formed of MgxZn1-xO (0?x<1) containing a p-type impurity; and which satisfies at least any one of the following conditions when the main surface is observed with an atomic force microscope: the density of observed hexagonal pits is not more than 5×106 pits/cm2; and no depressed portion, which includes multiple microcrystalline protrusions formed in the bottom portion of the depressed portion, is found in the main surface.
    Type: Application
    Filed: August 27, 2008
    Publication date: September 23, 2010
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Hiroyuki Yuki, Kentaro Tamura, Shunsuke Akasaka, Masashi Kawasaki, Akira Ohmoto, Atsushi Tsukazaki
  • Publication number: 20100230671
    Abstract: Provided are a ZnO-based semiconductor capable of alleviating the self-compensation effect and of achieving easier conversion into p-type, and a ZnO-based semiconductor device. The ZnO-based semiconductor includes a nitrogen-doped MgXZn1-XO (0<X<1) crystalline material. The ZnO-based semiconductor is subjected to a photoluminescence measurement performed at an absolute temperature of 12 Kelvin, and thus a spectrum distribution curve is obtained. The ZnO-based semiconductor is formed so that a peak intensity of the distribution curve obtained at 3.3 eV or larger is stronger than a peak intensity of the distribution curve obtained at 2.7 eV or smaller. Consequently, the self-compensation effect can be reduced and the conversion into p-type becomes easier.
    Type: Application
    Filed: September 26, 2008
    Publication date: September 16, 2010
    Inventors: Ken Nakahara, Shunsuke Akasaka, Hiroyuki Yuji, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Publication number: 20100224892
    Abstract: Provided is a nitride semiconductor light emitting element that has improved light extraction efficiency and a wide irradiation angle of outgoing light irrespective of the reflectance of a metal used for an electrode. An n side anti-reflection layer 2 and a p side Bragg reflection layer 4 are formed so as to sandwich an MQW active layer 3 that serves as a light emitting region, and the nitride semiconductor light emitting element has a double hetero structure. On top of the n side anti-reflection layer 2, an n electrode 1 is formed. Meanwhile, at the lower side of the p side Bragg reflection layer 4, a p electrode 5, a reflection film 7, and a pad electrode 8 are formed, and the pad electrode is bonded to a support substrate 10 with a conductive bonding layer 9 interposed in between. Both the n side anti-reflection layer 2 and the p side Bragg reflection layer 4 also serve as contact layers.
    Type: Application
    Filed: January 23, 2007
    Publication date: September 9, 2010
    Applicant: ROHM CO., LTD.
    Inventor: Ken Nakahara
  • Patent number: 7781791
    Abstract: In a semiconductor light emitting element, a p-type layer (220), an active layer (230) and an n-type layer (240) are laminated on a substrate in this order. The n-type layer (240) is formed with a rectangular n-side electrode (241) whose width in one direction is equal to that of the n-type layer (240). The thickness t of the n-type layer (240) satisfies Formula 1 below. The semiconductor light emitting element includes a side surface (270) extending in the lamination direction and formed with a plurality of projections (271). Supposing that the wavelength of the light from the active-layer (230) is ? and the index of refraction of the n-type layer (240) or the p-type layer (220) is n, the average WA of widths at bottoms of the projections is set to satisfy WA??/n.
    Type: Grant
    Filed: February 22, 2007
    Date of Patent: August 24, 2010
    Assignee: Rohm Co., Ltd.
    Inventors: Mitsuhiko Sakai, Tadahiro Okazaki, Ken Nakahara
  • Publication number: 20100183045
    Abstract: A substrate temperature measuring apparatus includes: a heating source that heat a substrate; a transmission window that transmits therethrough an infrared ray in a range of a wavelength at which the infrared ray cannot transmit through the substrate; and a temperature-measuring instrument having a sensitivity range including the range of the wavelength, and measuring a substrate temperature of the substrate by analyzing an infrared ray radiated from the substrate heated by the heating source and having transmitted through the transmission window.
    Type: Application
    Filed: July 22, 2008
    Publication date: July 22, 2010
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Patent number: 7745839
    Abstract: Provided are a double wavelength semiconductor light emitting device, having an n electrode and p electrode disposed on the same surface side, in which the area of a chip is reduced to increase the number of chips taken from one single wafer, in which light focusing performance of double wavelength optical beams are improved, and in which an active layer of a light emitting element having a longer wavelength can be prevented from deteriorating in a process of manufacturing; and a method of manufacturing the same. Semiconductor lasers D1 and D2 as two light emitting elements having different wavelengths are integrally formed on a common substrate 1. A semiconductor laminate A is deposited on an n-type contact layer 21 in a semiconductor laser D1, and a semiconductor laminate B is deposited in a semiconductor laser D2. The semiconductor laminate A and semiconductor laminate B are configured to have different layer structures.
    Type: Grant
    Filed: February 23, 2007
    Date of Patent: June 29, 2010
    Assignee: Rohm Co., Ltd.
    Inventors: Shinichi Tamai, Ken Nakahara, Atsushi Yamaguchi
  • Patent number: 7741637
    Abstract: Provided is a ZnO-based semiconductor device capable of growing a flat ZnO-based semiconductor layer on an MgZnO substrate having a main surface on the lamination side oriented in a c-axis direction. ZnO-based semiconductor layers 2 to 6 are epitaxially grown on an MgxZn1-xO (0?x<1) substrate 1 having a +C surface (0001), as a main surface, inclined at least in an m-axis direction. A p-electrode 8 is formed on the ZnO-based semiconductor layer 5, and an n-electrode 9 is formed on the underside of the MgxZn1-xO substrate 1. Thereby, steps regularly arranged in the m-axis direction can be formed on the surface of the MgxZn1-xO substrate 1, and a phenomenon called step bunching is prevented. Consequently, the flatness of a film of the semiconductor layers laminated on the substrate 1 can be improved.
    Type: Grant
    Filed: June 8, 2007
    Date of Patent: June 22, 2010
    Assignee: Rohm Co., Ltd.
    Inventors: Ken Nakahara, Hiroyuki Yuji, Kentaro Tamura, Shunsuke Akasaka, Masashi Kawasaki, Atsushi Tsukazaki, Akira Ohtomo
  • Publication number: 20100133470
    Abstract: Provided are a ZnO-based substrate having a surface suitable for crystal growth, and a method of manufacturing the ZnO-based substrate. The ZnO-based substrate is made in a way that almost no hydroxide groups exist on a crystal growth-side surface of a MgxZn1-xO substrate (0?x<1). To this end, as a method of treating the substrate, a final treatment to be applied on the crystal growth-side surface of the MgxZn1-xO substrate (0?x<1) is acidic wet etching at pH 3 or lower. Thereby, it is possible to prevent production of a hydroxide of Zn, and to reduce the density of crystal defects in a thin film formed on the ZnO-based substrate.
    Type: Application
    Filed: June 27, 2008
    Publication date: June 3, 2010
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Hiroyuki Yuji, Shunsuke Akasaka, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki
  • Patent number: 7718450
    Abstract: There is provided a method for manufacturing a nitride semiconductor device which has a p-type nitride semiconductor layer having a high carrier concentration (low resistance) by activating an acceptor without raising a problem of forming nitrogen vacancies which are generated when a high temperature annealing is carried out over an extended time. A semiconductor lamination portion (6) made of nitride semiconductor is formed on a substrate (1) so as to form a light emitting layer, and irradiated by a laser beam having a wavelength ? of ?=h·c/E or less (E is energy capable of separating off the bonding between Mg and H) from the front surface side of the semiconductor lamination portion. Then, a heat treatment is carried out at a temperature of 300 to 400° C.
    Type: Grant
    Filed: May 8, 2006
    Date of Patent: May 18, 2010
    Assignee: Rohm Co., Ltd.
    Inventor: Ken Nakahara
  • Publication number: 20100102309
    Abstract: To solve the foregoing problems, provided is a ZnO-based semiconductor element having an entirely novel function distinct from hitherto, using a ZnO-based semiconductor and organic matter for an active role. An organic electrode 2 is formed on a ZnO-based semiconductor 1, and an Au film 3 is formed on the organic electrode 2. An electrode formed of a multilayer metal film including a Ti film 4 and an Au film 5 is formed on the back surface of the ZnO-based semiconductor 1 so as to be opposed to the organic electrode 2. A bonding interface between the organic electrode 2 and the ZnO-based semiconductor 1 is in a pn junction-like state. Thus, rectification occurs therebetween.
    Type: Application
    Filed: February 4, 2008
    Publication date: April 29, 2010
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Hiroyuki Yuji, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki, Tomoteru Fukumura, Masaki Nakano
  • Publication number: 20100090214
    Abstract: Provided are an oxide thin film doped with an n-type impurity, and an oxide thin film device. In an oxide thin film (2), as shown in FIG. 1(b), doped oxide layers (2a) doped with an n-type (electron-conductivity type) impurity and undoped oxide layers (2b) not doped with an n-type impurity are laminated in an alternating and repeated manner. When an oxide layer is doped with the n-type impurity at a high concentration, roughness of a surface of the oxide layer becomes large. For this reason, the doped oxide layers (2a) are covered with the undoped oxide layers (2b) capable of ensuring surface flatness, before surface roughness attributable to the doped oxide layers (2a) becomes very large. Thus, a flat oxide thin film can be formed.
    Type: Application
    Filed: April 2, 2008
    Publication date: April 15, 2010
    Applicant: ROHM CO., LTD.
    Inventors: Ken Nakahara, Hiroyuki Yuji, Kentaro Tamura, Shunsuke Akasaka, Masashi Kawasaki, Akira Ohtomo, Atsushi Tsukazaki