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).
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Publication number: 20040213309Abstract: The nitride semiconductor layer structure comprises a buffer layer and a composite layer on the buffer layer. The buffer layer is a layer of a low-temperature-deposited nitride semiconductor material that includes AlN. The composite layer is a layer of a single-crystal nitride semiconductor material that includes AlN. The composite layer includes a first sub-layer adjacent the buffer layer and a second sub-layer over the first sub-layer. The single-crystal nitride semiconductor material of the composite layer has a first AlN molar fraction in the first sub-layer and has a second AlN molar fraction in the second sub-layer. The second AlN molar fraction is greater than the first AlN molar fraction. The nitride semiconductor laser comprises a portion of the above-described nitride semiconductor layer structure, and additionally comprises an optical waveguide layer over the composite layer and an active layer over the optical waveguide layer.Type: ApplicationFiled: December 19, 2001Publication date: October 28, 2004Inventors: Hiroshi Amano, Isamu Akasaki, Yawara Kaneko, Norihide Yamada, Tetsuya Takeuchi, Satoshi Watanabe
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Patent number: 6690700Abstract: A nitride semiconductor device that comprises a first layer, a second layer and a buffer layer sandwiched between the first layer and the second layer. The second layer is a layer of a single-crystal nitride semiconductor material including AlN and has a thickness greater than the thickness at which cracks would form if the second layer were grown directly on the first layer. The buffer layer is a layer of a low-temperature-deposited nitride semiconductor material that includes AlN. Incorporating the nitride semiconductor device into a semiconductor laser diode enables the laser diode to generate coherent light having a far-field pattern that exhibits a single peak.Type: GrantFiled: April 10, 2001Date of Patent: February 10, 2004Assignee: Agilent Technologies, Inc.Inventors: Tetsuya Takeuchi, Yawara Kaneko, Norihide Yamada, Hiroshi Amano, Isamu Akasaki
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Patent number: 6607595Abstract: Disclosed herein are (1) a light-emitting semiconductor device that uses a gallium nitride compound semiconductor (AlXGa1-xN) in which the n-layer of n-type gallium nitride compound semiconductor (AlxGa1-XN) is of double-layer structure including an n-layer of low carrier concentration and an n+-layer of high carrier concentration, the former being adjacent to the i-layer of insulating gallium nitride compound semiconductor (AlxGa1-xN); (2) a light-emitting semiconductor device of similar structure as above in which the i-layer is of double-layer structure including an iL-layer of low impurity concentration containing p-type impurities in comparatively low concentration and an iH-layer of high impurity concentration containing p-type impurities in comparatively high concentration, the former being adjacent to the n-layer; (3) a light-emitting semiconductor device having both of the above-mentioned features and (4) a method of producing a layer of an n-type gallium nitride compound semiconductor (AlxGa1-xType: GrantFiled: October 2, 2000Date of Patent: August 19, 2003Assignees: Toyoda Gosei Co., Ltd., Kabushiki Kaisha Toyota Chuo Kenkyu sho, Nagoya University, Japan Science and Technology CorporationInventors: Katsuhide Manabe, Akira Mabuchi, Hisaki Kato, Michinari Sassa, Norikatsu Koide, Shiro Yamazaki, Masafumi Hasimoto, Isamu Akasaki
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Patent number: 6593599Abstract: Disclosed herein are (1) a light-emitting semiconductor device that uses a gallium nitride compound semiconductor (AlxGa1−xN) in which the n-layer of n-type gallium nitride compound semiconductor (AlxGa1−xN) is of double-layer structure including an n-layer of low carrier concentration and an n+-layer of high carrier concentration, the former being adjacent to the i-layer of insulating gallium nitride compound semiconductor (AlxGa1−xN); (2) a light-emitting semiconductor device of similar structure as above in which the i-layer is of double-layer structure including an iL-layer of low impurity concentration containing p-type impurities in comparatively low concentration and an iH-layer of high impurity concentration containing p-type impurities in comparatively high concentration, the former being adjacent to the n-layer; (3) a light-emitting semiconductor device having both of the above-mentioned features and (4) a method of producing a layer of an n-type gallium nitride compound semicType: GrantFiled: October 14, 1999Date of Patent: July 15, 2003Assignees: Japan Science and Technology Corporation, Toyoda Gosei Co., Ltd., Nagoya UniversityInventors: Katsuhide Manabe, Akira Mabuchi, Hisaki Kato, Michinari Sassa, Norikatsu Koide, Shiro Yamazaki, Masafumi Hashimoto, Isamu Akasaki
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Patent number: 6569704Abstract: An optical semiconductor device having a plurality of GaN-based semiconductor layers containing a strained quantum well layer in which the strained quantum well layer has a piezoelectric field that depends on the orientation of the strained quantum well layer when the quantum layer is grown. In the present invention, the strained quantum well layer is grown with an orientation at which the piezoelectric field is less than the maximum value of the piezoelectric field strength as a function of the orientation. In devices having GaN-based semiconductor layers with a wurtzite crystal structure, the growth orientation of the strained quantum well layer is tilted at least 1° from the {0001} direction of the wurtzite crystal structure. In devices having GaN-based semiconductor layers with a zincblende crystal structure, the growth orientation of the strained quantum well layer is tilted at least 1° from the {111} direction of the zincblende crystal structure.Type: GrantFiled: November 21, 2000Date of Patent: May 27, 2003Assignee: Lumileds Lighting U.S., LLCInventors: Tetsuya Takeuchi, Norihide Yamada, Hiroshi Amano, Isamu Akasaki
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Patent number: 6537513Abstract: A substrate for fabricating semiconductor devices based on Group III semiconductors and the method for making the same. A substrate according to the present invention includes a base substrate, a first buffer layer, and a first single crystal layer. The first buffer layer includes a Group III material deposited on the base substrate at a temperature below that at which the Group III material crystallizes. The Group III material is crystallized by heating the buffer layer to a temperature above that at which the Group III material crystallizes to form a single crystal after the Group III material has been deposited. The first single crystal layer includes a Group III-V semiconducting material deposited on the first buffer layer at a temperature above that at which the Group III semiconducting material crystallizes. In one embodiment of the present invention, a second buffer layer and a second single crystal layer are deposited on the first single crystal layer.Type: GrantFiled: April 27, 2000Date of Patent: March 25, 2003Assignee: Lumileds Lighting U.S., LLCInventors: Hiroshi Amano, Tetsuya Takeuchi, Isamu Akasaki
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Patent number: 6534791Abstract: A nitride semiconductor epitaxial substrate includes a low-temperature-deposited buffer layer, the composition of which is AlxGa1−xN, where 0≦x≦1, and a single crystalline layer, the composition of which is AlyGa1−yN, where 0>y≦1. The single crystalline layer is deposited directly over the low-temperature-deposited buffer layer, wherein the buffer layer has a mole fraction x satisfying (y−0.3)≦x>y.Type: GrantFiled: September 6, 2001Date of Patent: March 18, 2003Assignee: Lumileds Lighting U.S., LLCInventors: Nobuaki Hayashi, Tetsuya Takeuchi, Hiroshi Amano, Isamu Akasaki
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Patent number: 6486068Abstract: A method for manufacturing a laser diode using Group III nitride compound semiconductor comprising a buffer layer 2, an n+ layer 3, a cladding layer 4, an active layer 5, a p-type cladding layer 61, a contact layer 62, an SiO2 layer 9, an electrode 7 which is formed on the window formed in a portion of the SiO2 layer 9, and an electrode 8 which is formed on a portion of the n+ layer 3 by etching a portion of 4 layers from the contact layer 62 down to the cladding layer 4. One pair of opposite facets S of a cavity is formed by RIBE, and then the facets are etched by gas cluster ion beam etching using Ar gas. As a result, the facets S are flatted and the mirror reflection of the facets S is improved.Type: GrantFiled: January 8, 1998Date of Patent: November 26, 2002Assignees: Toyoda Gosei Co., Ltd., Japan Science and TechnologyInventors: Shiro Yamasaki, Seiji Nagai, Masayoshi Koike, Isamu Akasaki, Hiroshi Amano, Isao Yamada, Jiro Matsuo
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Patent number: 6472689Abstract: Disclosed herein are (1) a light-emitting semiconductor device that uses a gallium nitride compound semiconductor (AlxGa1−xN) in which the n-layer of n-type gallium nitride compound semiconductor (AlxGa1−xN) is of double-layer structure including an n-layer of low carrier concentration and an n+-layer of high carrier concentration, the former being adjacent to the i-layer of insulating gallium nitride compound semiconductor (AlxGa1−xN); (2) a light-emitting semiconductor device of similar structure as above in which the i-layer is of double-layer structure including an iL-layer of low impurity concentration containing p-type impurities in comparatively low concentration and an iH-layer of high impurity concentration containing p-type impurities in comparatively high concentration, the former being adjacent to the n-layer; (3) a light-emitting semiconductor device having both of the above-mentioned features and (4) a method of producing a layer of an n-type gallium nitride compound semicType: GrantFiled: October 2, 2000Date of Patent: October 29, 2002Assignees: Toyoda Gosei Co., Ltd., Nagoya University, Japan Science and Technology CorporationInventors: Katsuhide Manabe, Akira Mabuchi, Hisaki Kato, Michinari Sassa, Norikatsu Koide, Shiro Yamazaki, Masafumi Hashimoto, Isamu Akasaki
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Patent number: 6472690Abstract: Disclosed herein are (1) a light-emitting semiconductor device that uses a gallium nitride compound semiconductor (AlxGa1−xN) in which the n-layer of n-type gallium nitride compound semiconductor (AlxGa1−xN) is of double-layer structure including an n-layer of low carrier concentration and an n+-layer of high carrier concentration, the former being adjacent to the i-layer of insulating gallium nitride compound semiconductor (AlxGa1−xN); (2) a light-emitting semiconductor device of similar structure as above in which the i-layer is of double-layer structure including an iL-layer of low impurity concentration containing p-type impurities in comparatively low concentration and an iH-layer of high impurity concentration containing p-type impurities in comparatively high concentration, the former being adjacent to the n-layer; (3) a light-emitting semiconductor device having both of the above-mentioned features and (4) a method of producing a layer of an n-type gallium nitride compound semicType: GrantFiled: October 2, 2000Date of Patent: October 29, 2002Assignees: Toyoda Gosei Co., Ltd., Nagoya University, Japan Science and Technology CorporationInventors: Katsuhide Manabe, Akira Mabuchi, Hisaki Kato, Michinari Sassa, Norikatsu Koide, Shiro Yamazaki, Masafumi Hashimoto, Isamu Akasaki
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Publication number: 20020094002Abstract: The nitride semiconductor layer structure comprises a buffer layer and a composite layer on the buffer layer. The buffer layer is a layer of a low-temperature-deposited nitride semiconductor material that includes AlN. The composite layer is a layer of a single-crystal nitride semiconductor material that includes AlN. The composite layer includes a first sub-layer adjacent the buffer layer and a second sub-layer over the first sub-layer. The single-crystal nitride semiconductor material of the composite layer has a first AlN molar fraction in the first sub-layer and has a second AlN molar fraction in the second sub-layer. The second AlN molar fraction is greater than the first AlN molar fraction. The nitride semiconductor laser comprises a portion of the above-described nitride semiconductor layer structure, and additionally comprises an optical waveguide layer over the composite layer and an active layer over the optical waveguide layer.Type: ApplicationFiled: December 19, 2001Publication date: July 18, 2002Inventors: Hiroshi Amano, Isamu Akasaki, Yawara Kaneko, Norihide Yamada, Tetsuya Takeuchi, Satoshi Watanabe
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Publication number: 20020084467Abstract: A method for fabricating a light-emitting semiconductor device including a III-Nitride quantum well layer includes selecting a facet orientation of the quantum well layer to control a field strength of a piezoelectric field and/or a field strength of a spontaneous electric field in the quantum well layer, and growing the quantum well layer with the selected facet orientation. The facet orientation may be selected to reduce the magnitude of a piezoelectric field and/or the magnitude of a spontaneous electric field, for example. The facet orientation may also be selected to control or reduce the magnitude of the combined piezoelectric and spontaneous electric field strength. As a result of the reduced magnitude of piezoelectric, spontaneous, or combined piezoelectric and spontaneous electric field strengths in their quantum well layers, light-emitting devices in accordance with the present invention may generate light with increased efficiency compared to prior art devices.Type: ApplicationFiled: November 13, 2001Publication date: July 4, 2002Inventors: Michael R. Krames, Tetsuya Takeuchi, Norihide Yamada, Hiroshi Amano, Isamu Akasaki
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Publication number: 20020060326Abstract: Disclosed herein are (1) a light-emitting semiconductor device that uses a gallium nitride compound semiconductor (AlxGa1-xN) in which the n-layer of n-type gallium nitride compound semiconductor (AlxGa1-xN) is of double-layer structure including an n-layer of low carrier concentration and an n+-layer of high carrier concentration, the former being adjacent to the i-layer of insulating gallium nitride compound semiconductor (AlxGa1-xN); (2) a light-emitting semiconductor device of similar structure as above in which the i-layer is of double-layer structure including an iL-layer of low impurity concentration containing p-type impurities in comparatively low concentration and an iH-layer of high impurity concentration containing p-type impurities in comparatively high concentration, the former being adjacent to the n-layer; (3) a light-emitting semiconductor device having both of the above-mentioned features and (4) a method of producing a layer of an n-type gallium nitride compound semiconductor (AlxGa1-xType: ApplicationFiled: January 23, 2002Publication date: May 23, 2002Inventors: Katsuhide Manabe, Akira Mabuchi, Hisaki Kato, Michinari Sassa, Norikatsu Koide, Shiro Yamazaki, Masafumi Hashimoto, Isamu Akasaki
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Patent number: 6362017Abstract: Disclosed herein are (1) a light-emitting semiconductor device that uses a gallium nitride compound semiconductor (AlxGa1−xN) in which the n-layer of n-type gallium nitride compound semiconductor (AlxGa1−xN) is of double-layer structure including an n-layer of low carrier concentration and an n+-layer of high carrier concentration, the former being adjacent to the i-layer of insulating gallium nitride compound semiconductor (AlxGa1−xN); (2) a light-emitting semiconductor device of similar structure as above in which the i-layer is of double-layer structure including an iL-layer of low impurity concentration containing p-type impurities in comparatively low concentration and an iH-layer of high impurity concentration containing p-type impurities in comparatively high concentration, the former being adjacent to the n-layer; (3) a light-emitting semiconductor device having both of the above-mentioned features and (4) a method of producing a layer of an n-type gallium nitride compound semicType: GrantFiled: June 2, 2000Date of Patent: March 26, 2002Assignees: Toyoda Gosei Co., Ltd., Nagoya University, Japan Science and Technology CorporationInventors: Katsuhide Manabe, Akira Mabuchi, Hisaki Kato, Michinari Sassa, Norikatsu Koide, Shiro Yamazaki, Masafumi Hashimoto, Isamu Akasaki
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Publication number: 20020006726Abstract: A method for manufacturing a laser diode using Group III nitride compound semiconductor comprising a buffer layer 2, an n+ layer 3, a cladding layer 4, an active layer 5, a p-type cladding layer 61, a contact layer 62, an SiO2 layer 9, an electrode 7 which is formed on the window formed in a portion of the SiO2 layer 9, and an electrode 8 which is formed on a portion of the n+ layer 3 by etching a portion of 4 layers from the contact layer 62 down to the cladding layer 4. One pair of opposite facets S of a cavity is formed by RIBE, and then the facets are etched by gas cluster ion beam etching using Ar gas. As a result, the facets S are flatted and the mirror reflection of the facets S is improved.Type: ApplicationFiled: January 8, 1998Publication date: January 17, 2002Inventors: SHIRO YAMASAKI, SEIJI NAGAI, MASAYOSHI KOIKE, ISAMU AKASAKI, HIROSHI AMANO, ISAO YAMADA, JIRO MASUO
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Publication number: 20010038656Abstract: A nitride semiconductor device that comprises a first layer, a second layer and a buffer layer sandwiched between the first layer and the second layer. The second layer is a layer of a single-crystal nitride semiconductor material including AlN and has a thickness greater than the thickness at which cracks would form if the second layer were grown directly on the first layer. The buffer layer is a layer of a low-temperature-deposited nitride semiconductor material that includes AlN. Incorporating the nitride semiconductor device into a semiconductor laser diode enables the laser diode to generate coherent light having a far-field pattern that exhibits a single peak.Type: ApplicationFiled: April 10, 2001Publication date: November 8, 2001Inventors: Tetsuya Takeuchi, Yawara Kaneko, Norihide Yamada, Hiroshi Amano, Isamu Akasaki
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Publication number: 20010010372Abstract: An optical semiconductor device having a plurality of GaN-based semiconductor layers containing a strained quantum well layer in which the strained quantum well layer has a piezoelectric field that depends on the orientation of the strained quantum well layer when the quantum layer is grown. In the present invention, the strained quantum well layer is grown with an orientation at which the piezoelectric field is less than the maximum value of the piezoelectric field strength as a function of the orientation. In devices having GaN-based semiconductor layers with a wurtzite crystal structure, the growth orientation of the strained quantum well layer is tilted at least 1° from the {0001} direction of the wurtzite crystal structure. In devices having GaN-based semiconductor layers with a zincblende crystal structure, the growth orientation of the strained quantum well layer is tilted at least 1° from the {111} direction of the zincblende crystal structure.Type: ApplicationFiled: March 20, 2001Publication date: August 2, 2001Inventors: Tetsuya Takeuchi, Norihide Yamada, AichiHiroshi Amano, Isamu Akasaki
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Patent number: 6249012Abstract: A semiconductor device having an n-type layer of gallium nitride that is doped with silicon and has a resistively ranging from 3×10−1 &OHgr;cm to 8×10−3 &OHgr;cm or a carrier concentration ranging from 6×1016/cm3 to 3×1018/cm3.Type: GrantFiled: October 23, 1997Date of Patent: June 19, 2001Assignees: Toyoda Gosei Co., Ltd., Nagoya University, Japan Science and Technology CorporationInventors: Katsuhide Manabe, Akira Mabuchi, Hisaki Kato, Michinari Sassa, Norikatsu Koide, Shiro Yamazaki, Masafumi Hashimoto, Isamu Akasaki
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Patent number: 6229151Abstract: An optical semiconductor device having a plurality of GaN-based semiconductor layers containing a strained quantum well layer in which the strained quantum well layer has a piezoelectric field that depends on the orientation of the strained quantum well layer when the quantum layer is grown. In the present invention, the strained quantum well layer is grown with an orientation at which the piezoelectric field is less than the maximum value of the piezoelectric field strength as a function of the orientation. In devices having GaN-based semiconductor layers with a wurtzite crystal structure, the growth orientation of the strained quantum well layer is tilted at least 1° from the {0001} direction of the wurtzite crystal structure. In devices having GaN-based semiconductor layers with a zincblende crystal structure, the growth orientation of the strained quantum well layer is tilted at least 1° from the {111} direction of the zincblende crystal structure.Type: GrantFiled: September 29, 1998Date of Patent: May 8, 2001Assignee: Agilent Technologies, Inc.Inventors: Tetsuya Takeuchi, Norihide Yamada, Hiroshi Amano, Isamu Akasaki
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Patent number: 6188087Abstract: A novel light-emitting device includes a sapphire substrate with a light-emitting layer comprising InXGa1−XN, where the critical value of the indium mole fraction X is determined by a newly derived relationship between the indium mole fraction X and the wavelength &lgr; of emitted light.Type: GrantFiled: September 8, 1997Date of Patent: February 13, 2001Assignees: Toyoda Gosei Co., Ltd, Isamu Akasaki, Hiroshi AmanoInventors: Norikatsu Koide, Masayoshi Koike, Shiro Yamasaki, Isamu Akasaki, Hiroshi Amano