Patents by Inventor Yuji Ohkura
Yuji Ohkura 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).
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Publication number: 20020196828Abstract: In a semiconductor laser device including a window structure region formed by disordering an active layer or active layers of a quantum well structure by silicon ion implantation and a subsequent heat treatment, a dislocation loop is substantially absent in the window structure region and the vicinity thereof (upper clad layer). Accordingly, deterioration of the semiconductor laser device induced by dislocation loops can be prevented, and reliability of the semiconductor laser device can be improved.Type: ApplicationFiled: May 2, 2002Publication date: December 26, 2002Applicant: Mitsubishi Denki Kabushiki KaishaInventors: Shinji Abe, Tetsuya Yagi, Motoharu Miyashita, Harumi Nishiguchi, Yuji Ohkura, Nobuyuki Kasai, Yoshihisa Tashiro, Junji Tanimura
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Patent number: 6333946Abstract: A forward mesa ridge-embedded semiconductor laser device provides a high power output and includes a base portion of a forward mesa ridge having a narrow width to stabilize transverse mode oscillation and an upper cladding layer having a thickness sufficient to reduce loss of the laser beam, a top portion of the forward mesa ridge being interposed between parts of the current blocking layer to reduce the device resistance. The upper cladding layer includes a first cladding layer having the forward mesa ridge and a second cladding layer opposite the first cladding layer. The second cladding layer is deposited over the first cladding layer through the forward mesa ridge and a current blocking layer is positioned on both sides of the forward mesa ridge.Type: GrantFiled: August 10, 1999Date of Patent: December 25, 2001Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Motoharu Miyashita, Harumi Nishiguchi, Akihiro Shima, Yuji Ohkura
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Patent number: 6154476Abstract: A semiconductor laser diode includes a p-type GaAs semiconductor substrate, a p-type region which includes a p-type AlGaAs lower cladding layer, an active layer and an n-type region which includes an n-type AlGaAs upper cladding layer, wherein the n-type AlGaAs upper cladding layer is Al.sub.x Ga.sub.1-x As (x.gtoreq.0.4) having a carrier concentration of no more than 6.times.10.sup.17 cm.sup.-3.Type: GrantFiled: March 25, 1998Date of Patent: November 28, 2000Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Harumi Nishiguchi, Yuji Ohkura
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Patent number: 5887011Abstract: A semiconductor laser includes a first conductivity type GaAs substrate; a AlGaAs double heterojunction structure disposed on the GaAs substrate and including an upper cladding layer having a mesa ridge stripe with a side surface that makes an angle larger than 90.degree. with a front surface of the upper cladding layer; a first current blocking layer of first conductivity type AlGaAs; and a second current blocking layer of first conductivity type AlGaAs, the first and second current blocking layers covering the mesa ridge stripe. The Al compositions of the first and second current blocking layers are larger than that of the upper cladding layer, maintaining an equivalent refractive index of an active region higher than that of other portions of the semiconductor laser. As a result, the differences between the lattice constant of the second current blocking layer and the GaAs substrate or the AlGaAs upper cladding layer are smaller than in prior art semiconductor lasers.Type: GrantFiled: February 18, 1997Date of Patent: March 23, 1999Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Yuji Ohkura, Motoharu Miyashita, Shoichi Karakida
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Patent number: 5835516Abstract: A method of fabricating a semiconductor laser device includes successively forming an active layer and upper cladding layers on a lower cladding layer, etching and removing portions except regions of the upper cladding layers where a current is to flow to form a stripe-shaped ridge structure, and forming a buffer layer comprising Al.sub.x Ga.sub.1-x As having an Al composition ratio x of 0 to 0.3 on a surface of the upper cladding layers exposed by the etching and forming a current blocking layer of first conductivity type Al.sub.y Ga.sub.1-y As having an Al composition ratio y of at least 0.5 on the buffer layer to bury portions of the upper cladding layers which are not removed by the etching process. Therefore, since the layer grown on the upper cladding layer exposed by etching of AlGaAs or GaAs having a low Al composition ratio (0-0.3), three-dimensional growth of and crystalline defects in the buffer layer are suppressed.Type: GrantFiled: December 8, 1995Date of Patent: November 10, 1998Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Motoharu Miyashita, Hirotaka Kizuki, Yasuaki Yoshida, Yutaka Mihashi, Yasutomo Kajikawa, Shoichi Karakida, Yuji Ohkura
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Patent number: 5800622Abstract: In a thermal radiation type substrate heating system of an MOCVD growth apparatus, a susceptor includes a semi-circular concavity is formed in each of wafer pockets at the forward area in a wafer rotation direction so that P-richness in a crystalline film grown at the gas upstream area is suppressed. Specifically, the conventional wafer holder exhibits a non-uniform temperature distribution so that the surface temperature is high at the gas upstream area and low at the downstream area. On the other hand, the structure according to the present invention realizes a high temperature at a wafer contact area and a low temperature at a wafer non-contact area, thus leading to a uniform surface temperature over the entire gas upstream and downstream areas.Type: GrantFiled: January 30, 1996Date of Patent: September 1, 1998Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Masayoshi Takemi, Yuji Ohkura
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Patent number: 5706304Abstract: A semiconductor laser device includes a first conductivity type GaAs substrate; a first conductivity type first lower cladding layer disposed on the GaAs substrate, lattice-matching with the GaAs substrate, and having an energy band gap; a first conductivity type AlGaAs second lower cladding layer disposed on the first lower cladding layer and having an energy band gap larger than the energy band gap of the first lower cladding layer; an active layer disposed on the second lower cladding layer and having an energy band gap smaller than the energy band gap of the first lower cladding layer; a second conductivity type AlGaAs second upper cladding layer disposed on the active layer and having an energy band gap; a second conductivity type first upper cladding layer disposed on the second upper cladding layer, lattice-matching with the GaAs substrate, and having an energy band gap larger than the energy band gap of the active layer and smaller than the energy band gap of the second upper cladding layer; a secondType: GrantFiled: February 20, 1996Date of Patent: January 6, 1998Assignee: Mitsubishi Denki Kabushiki KaishaInventor: Yuji Ohkura
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Patent number: 5602414Abstract: In a method for fabricating an infrared detector, initially, a CdHgTe layer of a first conductivity type is produced on a front surface of a semiconductor substrate, a plurality of spaced apart CdHgTe regions of a second conductivity type, opposite the first conductivity type, are produced at the surface of the first conductivity type CdHgTe layer, and part of the surface of the first conductivity type CdHgTe layer between the second conductivity type CdHgTe regions is selectively irradiated with a charged particle beam to evaporate Hg atoms from that part, whereby a CdHgTe separation region of the first conductivity type and having a Cd composition larger than that of the first conductivity type CdHgTe layer is produced penetrating through the first conductivity type CdHgTe layer and surrounding each of the second conductivity type CdHgTe regions. Therefore, a highly-integrated high-resolution infrared detector with no crosstalk between pixels is achieved.Type: GrantFiled: June 16, 1994Date of Patent: February 11, 1997Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Kotaro Mitsui, Zenpei Kawazu, Kazuo Mizuguchi, Seiji Ochi, Yuji Ohkura, Norio Hayafuji, Hirotaka Kizuki, Mari Tsugami, Akihiro Takami, Manabu Katoh
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Patent number: 5386433Abstract: A single wavelength oscillating semiconductor laser device having at least two diffraction gratings in an active region in which the order of a first diffraction grating disposed in the center of the laser is higher than that of a second diffraction grating disposed in the neighborhood of resonator facets.Type: GrantFiled: May 10, 1993Date of Patent: January 31, 1995Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Yuji Ohkura, Masatoshi Fujiwara
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Patent number: 5238785Abstract: A method for manufacturing a diffraction grating includes applying a resist, the developing speed of which has an extreme at a certain exposure intensity, to a substrate on which the diffraction grating is to be formed, performing interference exposure of the resist with maximum and minimum values of exposure intensity respectively larger and smaller than the intensity which makes the developing speed an extreme, developing the resist, and etching the substrate using the remaining resist as a mask.Type: GrantFiled: August 17, 1990Date of Patent: August 24, 1993Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Yuji Ohkura, Masatoshi Fujiwara
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Patent number: 5198370Abstract: In a method of producing an infrared detector, a first conductivity type semiconductor layer, in which lattice vacancies acting as first conductivity type carriers are formed by evaporation of an element during annealing, is formed on a substrate and dopant impurities producing a second conductivity type are diffused in an annealing step from the impurity layer into the first conductivity type semiconductor layer to form pixel regions. During the diffusion, the surface of the first conductivity type compound semiconductor layer corresponding to non-pixel regions is exposed. In the regions of the first conductivity type semiconductor layer which becomes non-pixel regions, the first conductivity type carrier concentration increases due to the lattice vacancies generated by the evaporation of an element and, even when the dopant impurity is diffused into these regions, these regions remain first conductivity type regions.Type: GrantFiled: February 4, 1992Date of Patent: March 30, 1993Assignee: Mitsubishi Denki Kabushiki KaishaInventors: Yuji Ohkura, Tohru Takiguchi
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Patent number: 4847857Abstract: In a single wavelength oscillation semiconductor laser having a diffraction grating at the active region, the coupling coefficient between the light and the diffraction grating is low within the laser and high in the neighborhood of the resonator end surface. The amplitude of the diffraction grating is low within the laser and high in the neighborhood of the resonator end surface, or the active layer or the guide layer is thick within the laser and thin in the neighborhood of the resonator end surface. Thus, the laser oscillates at a single wavelength even at high power output operation.Type: GrantFiled: July 7, 1988Date of Patent: July 11, 1989Assignee: Mitsubishi Denki Kabushiki KaishaInventor: Yuji Ohkura