Patents by Inventor Rajaram Bhat
Rajaram Bhat 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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Patent number: 7983317Abstract: Multi-quantum well laser structures are provided comprising active and/or passive MQW regions. Each of the MQW regions comprises a plurality of quantum wells and intervening barrier layers. Adjacent MQW regions are separated by a spacer layer that is thicker than the intervening barrier layers. The bandgap of the quantum wells is lower than the bandgap of the intervening barrier layers and the spacer layer. The active region may comprise active and passive MQWs and be configured for electrically-pumped stimulated emission of photons or it may comprises active MQW regions configured for optically-pumped stimulated emission of photons.Type: GrantFiled: December 16, 2008Date of Patent: July 19, 2011Assignee: Corning IncorporatedInventors: Rajaram Bhat, Jerome Napierala, Dmitry Sizov, Chung-En Zah
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Patent number: 7965752Abstract: A semiconductor laser device operable to emit light having a desired wavelength in the green spectral range. The semiconductor laser device may include a pumping source and a laser structure including a substrate, a first cladding layer, and one or more active region layers. The one or more active region layers include a number of quantum wells having a spontaneous emission peak wavelength that is greater than about 520 nm at a reference pumping power density. The pumping source is configured to pump each quantum well at a pumping power density such that a stimulated emission peak of each quantum well is within the green spectral range, and the number of quantum wells within the one or more active region layers is such that a net optical gain of the quantum wells is greater than a net optical loss coefficient at the desired wavelength in the green spectral range.Type: GrantFiled: November 30, 2009Date of Patent: June 21, 2011Assignee: Corning IncorporatedInventors: Rajaram Bhat, Chad Stephen Gallinat, Jerome Napierala, Dmitry Sizov, Chung-En Zah
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Publication number: 20110136280Abstract: A method of manufacturing an optoelectronic light emitting semiconductor device is provided where a Multi-quantum Well (MQW) subassembly is subjected to reduced temperature vapor deposition processing to form one or more of n-type or p-type layers over the MQW subassembly utilizing a plurality of precursors and an indium surfactant. The precursors and the indium surfactant are introduced into the vapor deposition process at respective flow rates with the aid of one or more carrier gases, at least one of which comprises H2. The indium surfactant comprises an amount of indium sufficient to improve crystal quality of the p-type layers formed during the reduced temperature vapor deposition processing and the respective precursor flow rates and the H2 content of the carrier gas are selected to maintain a mole fraction of indium from the indium surfactant to be less than approximately 1% in the n-type or p-type layers.Type: ApplicationFiled: December 8, 2009Publication date: June 9, 2011Inventor: Rajaram Bhat
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Publication number: 20110128984Abstract: A semiconductor laser device operable to emit light having a desired wavelength in the green spectral range. The semiconductor laser device may include a pumping source and a laser structure including a substrate, a first cladding layer, and one or more active region layers. The one or more active region layers include a number of quantum wells having a spontaneous emission peak wavelength that is greater than about 520 nm at a reference pumping power density. The pumping source is configured to pump each quantum well at a pumping power density such that a stimulated emission peak of each quantum well is within the green spectral range, and the number of quantum wells within the one or more active region layers is such that a net optical gain of the quantum wells is greater than a net optical loss coefficient at the desired wavelength in the green spectral range.Type: ApplicationFiled: November 30, 2009Publication date: June 2, 2011Inventors: Rajaram Bhat, Chad Stephen Gallinat, Jerome Napierala, Dmitry Sizov, Chung-En Zah
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Publication number: 20110049469Abstract: An optoelectronic light emitting semiconductor device is provided comprising an active region, a p-type Group III nitride layer, an n-type Group III nitride layer, a p-side metal contact layer, an n-side metal contact layer, and an undoped tunneling enhancement layer. The p-side metal contact layer is characterized by a work function W satisfying the following relation: W?e?AFF±0.025 eV where e?AFF is the electron affinity of the undoped tunneling enhancement layer. The undoped tunneling enhancement layer and the p-type Group III nitride layer comprise conduction and valence energy bands. The top of the valence band V1 of the undoped tunneling enhancement layer is above the top of the valence band V2 of the p-type Group III nitride layer at the band offset interface to generate a capacity for a relatively high concentration of holes in the undoped tunneling enhancement layer at the band offset interface. Additional embodiments are disclosed and claimed.Type: ApplicationFiled: September 3, 2009Publication date: March 3, 2011Inventors: Rajaram Bhat, Jerome Napierala, Dmitry Sizov, Jingqun Xi, Chung-En Zah
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Publication number: 20100150193Abstract: Multi-quantum well laser structures are provided comprising active and/or passive MQW regions. Each of the MQW regions comprises a plurality of quantum wells and intervening barrier layers. Adjacent MQW regions are separated by a spacer layer that is thicker than the intervening barrier layers. The bandgap of the quantum wells is lower than the bandgap of the intervening barrier layers and the spacer layer. The active region may comprise active and passive MQWs and be configured for electrically-pumped stimulated emission of photons or it may comprises active MQW regions configured for optically-pumped stimulated emission of photons.Type: ApplicationFiled: December 16, 2008Publication date: June 17, 2010Inventors: Rajaram Bhat, Jerome Napierala, Dmitry Sizov, Chung-En Zah
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Patent number: 7615389Abstract: Ga(In)N-based laser structures and related methods of fabrication are proposed where Ga(In)N-based semiconductor laser structures are formed on AlN or GaN substrates in a manner that addresses the need to avoid undue tensile strain in the semiconductor structure. In accordance with one embodiment of the present invention, a Ga(In)N-based semiconductor laser is provided on an AlN or GaN substrate provided with an AlGaN lattice adjustment layer where the substrate, the lattice adjustment layer, the lower cladding region, the active waveguiding region, the upper cladding region, and the N and P type contact regions of the laser form a compositional continuum in the semiconductor laser. Additional embodiments are disclosed and claimed.Type: GrantFiled: August 15, 2007Date of Patent: November 10, 2009Assignee: Corning IncorporatedInventors: Rajaram Bhat, Jerome Napierala, Dmitry Sizov, Chung-En Zah
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Publication number: 20090101924Abstract: Methods and apparatus for producing a gallium nitride semiconductor on insulator structure include: bonding a single crystal silicon layer to a transparent substrate; and growing a single crystal gallium nitride layer on the single crystal silicon layer.Type: ApplicationFiled: October 18, 2007Publication date: April 23, 2009Inventors: Rajaram Bhat, Kishor Purushottam Gadkaree, Jerome Napierala, Linda Ruth Pinckney, Chung-En Zah
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Publication number: 20080299691Abstract: Ga(In)N-based laser structures and related methods of fabrication are proposed where Ga(In)N-based semiconductor laser structures are formed on AlN or GaN substrates in a manner that addresses the need to avoid undue tensile strain in the semiconductor structure. In accordance with one embodiment of the present invention, a Ga(In)N-based semiconductor laser is provided on an AlN or GaN substrate provided with an AlGaN lattice adjustment layer where the substrate, the lattice adjustment layer, the lower cladding region, the active waveguiding region, the upper cladding region, and the N and P type contact regions of the laser form a compositional continuum in the semiconductor laser. Additional embodiments are disclosed and claimed.Type: ApplicationFiled: August 15, 2007Publication date: December 4, 2008Inventors: Rajaram Bhat, Jerome Napierala, Dmitry Sizov, Chung-En Zah
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Patent number: 6982439Abstract: A tunnel junction device (102) with minimal hydrogen passivation of acceptors includes a p-type tunnel junction layer (106) of a first semiconductor material doped with carbon. The first semiconductor material includes aluminum, gallium, arsenic and antimony. An n-type tunnel junction layer (104) of a second semiconductor material includes indium, gallium, arsenic and one of aluminum and phosphorous. The junction between the p-type and an-type tunnel junction layers forms a tunnel junction (110).Type: GrantFiled: May 17, 2005Date of Patent: January 3, 2006Assignee: Corning IncoporatedInventors: Rajaram Bhat, Nobuhiko Nishiyama
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Publication number: 20050253164Abstract: A tunnel junction device (102) with minimal hydrogen passivation of acceptors includes a p-type tunnel junction layer (106) of a first semiconductor material doped with carbon. The first semiconductor material includes aluminum, gallium, arsenic and antimony. An n-type tunnel junction layer (104) of a second semiconductor material includes indium, gallium, arsenic and one of aluminum and phosphorous. The junction between the p-type and an-type tunnel junction layers forms a tunnel junction (110).Type: ApplicationFiled: May 17, 2005Publication date: November 17, 2005Inventors: Rajaram Bhat, Nobuhiko Nishiyama
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Patent number: 6933539Abstract: A tunnel junction device (102) with minimal hydrogen passivation of acceptors includes a p-type tunnel junction layer (106) of a first semiconductor material doped with carbon. The first semiconductor material includes aluminum, gallium, arsenic and antimony. An n-type tunnel junction layer (104) of a second semiconductor material includes indium, gallium, arsenic and one of aluminum and phosphorous. The junction between the p-type and an-type tunnel junction layers forms a tunnel junction (110).Type: GrantFiled: May 17, 2004Date of Patent: August 23, 2005Assignee: Corning IncorporatedInventors: Rajaram Bhat, Nobuhiko Nishiyama
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Publication number: 20050112281Abstract: A method for growing a dilute nitride includes placing a III-V substrate 120 in a chemical reaction chamber 125. The III-V substrate 120 is heated to a predetermined temperature in a range about 550-700 degree C. in an atmosphere including a Group V element gas or vapor 187. Vapors of at least one Group III element organometallic compound 135, 150, 162 are flowed into the chemical reaction chamber for initiating an epitaxial growth. Vapors of a Group III element containing compound 172 wherein at least one Group III element is covalently bonded with nitrogen (N) are also flowed to grow dilute nitride films on the III-V substrate inside the chamber 125.Type: ApplicationFiled: November 21, 2003Publication date: May 26, 2005Inventor: Rajaram Bhat
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Patent number: 6285044Abstract: A heterojunction bipolar transistor based on the InP/InGaAs materials family and its method of making. An n-type collector layer, principally composed of InP is epitaxially grown on an insulating InP substrate by vapor phase epitaxy. The collector layer is then laterally defined into a stack, and semi-insulating InP is regrown around the sides of the stack to the extent that it planarizes with the stack top. The semi-insulating InP electrically isolates the collector stack. A thin base layer of p-type InGaAs, preferably lattice matched to InP, is grown over the collector stack, and n-type emitter layer is grown over the base layer. A series of photolithographic steps then defines a small emitter stack and a base that extends outside of the area of the emitter and collector stacks. The reduced size of the interface between the base and the collector produces a lower base-collector capacitance and hence higher speed of operation for the transistor.Type: GrantFiled: April 14, 1999Date of Patent: September 4, 2001Assignee: Telcordia Technologies, Inc.Inventor: Rajaram Bhat
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Patent number: 5946582Abstract: A heterojunction bipolar transistor based on the InP/InGaAs materials family and its method of making. An n-type collector layer, principally composed of InP is epitaxially grown on an insulating InP substrate by vapor phase epitaxy. The collector layer is then laterally defined into a stack, and semi-insulating InP is regrown around the sides of the stack to the extent that it planarizes with the stack top. The semi-insulating InP electrically isolates the collector stack. A thin base layer of p-type InGaAs, preferably lattice matched to InP, is grown over the collector stack, and an n-type emitter layer is grown over the base layer. A series of photolithographic steps then defines a small emitter stack and a base that extends outside of the area of the emitter and collector stacks. The reduced size of the interface between the base and the collector produces a lower base-collector capacitance and hence higher speed of operation for the transistor.Type: GrantFiled: June 12, 1997Date of Patent: August 31, 1999Assignee: Telcordia Technologies, Inc.Inventor: Rajaram Bhat
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Patent number: 5882951Abstract: An InP-based opto-electronic integrated circuit including an active layer having one or more quantum wells (36, 38). According to the invention, a barrier layer (34) of AlGaInAs is formed, preferably between the quantum wells and the substrate (30) to prevent the migration of species from the substrate and lower InP layers that tend to shift the emission wavelengths of the quantum wells to shorter wavelengths, i.e., a blue shift. The barrier layer can be patterned so that some areas of the quantum wells exhibit blue shifting to a shorter wavelength while other areas retain their longer wavelength during annealing.Type: GrantFiled: June 18, 1997Date of Patent: March 16, 1999Assignee: Bell Communications Research, Inc.Inventor: Rajaram Bhat
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Patent number: 5802232Abstract: A waveguide having alternating regions of different crystallographic orientations, thereby providing quasi-phase-matching for a non-linear frequency conversion, in which two wafers with epitaxial layers thereon are bonded together having different, preferably opposed, crystallographic orientations. One wafer is etched away, and a grating is etched such that one part of the grating has the orientation of one wafer and the other part has the orientation of the other wafer. Thereafter, a waveguide structure is epitaxially deposited upon the differentially oriented template so that the waveguide is differentially oriented in its axial direction. Thereby, quasi-phase-matching non-linear effects can be achieved.Type: GrantFiled: February 16, 1996Date of Patent: September 1, 1998Assignee: Bell Communications Research, Inc.Inventors: Rajaram Bhat, Catherine Genevieve Caneau, Mark A. Koza, Sung-Joo Yoo
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Patent number: 5796902Abstract: A waveguide having alternating regions of different crystallographic orientations, thereby providing quasi-phase-matching for a non-linear frequency conversion, in which two wafers with or without epitaxial layers thereon are bonded together having different, preferably opposed, crystallographic orientations. One wafer is etched away, and a grating is etched such that one part of the grating has the orientation of one wafer and the other part has the orientation of the other wafer. Thereafter, a waveguide structure is epitaxially deposited upon the differentially oriented template so that the waveguide is differentially oriented in its axial direction. Thereby, quasi-phase-matching non-linear effects can be achieved. Several important devices can thereby be achieved, including a coherent optical source using frequency doubling and a frequency converter useful in wavelength division multiplexed communication, as well as others.Type: GrantFiled: July 5, 1996Date of Patent: August 18, 1998Assignee: Bell Communications Research, Inc.Inventors: Rajaram Bhat, Catherine Caneau, Mark A. Koza, Sung Joo Yoo
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Patent number: 5771256Abstract: An InP-based opto-electronic integrated circuit including an active layer having one or more quantum wells (36, 38). According to the invention, a barrier layer (34) of AlGaInAs is formed, preferably between the quantum wells and the substrate (30) to prevent the migration of species from the substrate and lower InP layers that tend to shift the emission wavelengths of the quantum wells to shorter wavelengths, i.e., a blue shift. The barrier layer can be patterned so that some areas of the quantum wells exhibit blue shifting to a shorter wavelength while other areas retain their longer wavelength during annealing.Type: GrantFiled: June 3, 1996Date of Patent: June 23, 1998Assignee: Bell Communications Research, Inc.Inventor: Rajaram Bhat
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Patent number: 5541949Abstract: A diode laser (2) including multiple quantum wells (26) of AlGaInAs in either compressive or tensile strain and barrier layers (28), wherein the conduction band confines the electron preferably to at least 150 meV, or at least 135 meV, such that the diode laser is efficient and can operate for extended periods at elevated temperatures up to 85.degree. C. and above.Type: GrantFiled: January 30, 1995Date of Patent: July 30, 1996Assignee: Bell Communications Research, Inc.Inventors: Rajaram Bhat, Chung-En Zah