Patents by Inventor Alfred Y. Cho
Alfred Y. Cho 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: 5633193Abstract: Heteroepitaxial growth of phosphorus-containing III/V semiconductor material (e.g., InGaAsP) on a non-planar surface of a different phosphorus-containing III/V semiconductor material (e.g., InP) is facilitated by heating the non-planar surface in a substantially evacuated chamber to a mass-transport temperature, and exposing the surface to a flux of at least phosphorus form a solid phosphorus source. This mass-transport step is followed by in situ growth of the desired semiconductor material, with at least an initial portion of the growth being done at a first growth temperature that is not greater than the mass transport temperature. Growth typically is completed at a second growth temperature higher than the first growth temperature. A significant aspect of the method is provision of the required fluxes (e.g., phosphorus, arsenic, indium, gallium) from solid sources, resulting in hydrogen-free mass transport and growth, which can be carried out at lower temperatures than is customary in the prior art.Type: GrantFiled: May 22, 1996Date of Patent: May 27, 1997Assignee: Lucent Technologies Inc.Inventors: James N. Baillargeon, Alfred Y. Cho, Sung-Nee G. Chu, Wen-Yen Hwang
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Patent number: 5588969Abstract: In accordance with the invention, phosphorous vapor is provided by in situ conversion of red phosphorous to white phosphorous and permitting the flow of vapor from said white phosphorous. The conversion is effected in a low pressure cell having a high temperature region for evaporating red phosphorous and a low temperature region for condensing the resulting vapor into white phosphorous. At room temperature equilibrium, the vapor pressure is dominated by the white phosphorous.Type: GrantFiled: March 29, 1995Date of Patent: December 31, 1996Assignee: Lucent Technologies Inc.Inventors: James N. Baillargeon, Alfred Y. Cho
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Patent number: 5570386Abstract: The disclosed unipolar quantum cascade (QC) laser comprises a multiplicity of essentially identical active regions, with adjacent active regions separated by a superlattice carrier injection/relaxation region. A given active region contains a single quantum well with at least two electron states. Lasing is obtained without global intersubband population inversion. Instead, there is believed to exist local population inversion in a small region of k-space near k=0, corresponding to electron energies approximately within an optical phonon energy (.about.35 meV) from the bottom of the lower subband. A novel design feature that can be used to improve the thermal characteristics of substantially any QC laser is also disclosed.Type: GrantFiled: July 31, 1995Date of Patent: October 29, 1996Assignee: Lucent Technologies Inc.Inventors: Federico Capasso, Alfred Y. Cho, Jerome Faist, Albert L. Hutchinson, Carlo Sirtori, Deborah L. Sivco
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Patent number: 5550854Abstract: A laser having a binary stratified structure of alternating sections of graded-index, separate confinement heterostructure (GRINSCH) and semi-insulating semiconductor formed in the direction of light propagation. The active region of the laser includes at least two GRINSCH sections upon a substrate and at least three filler sections sandwiching the at least two GRINSCH sections in an alternating fashion. An analysis of the practical limit on the minimum threshold current and the packaging problems of a semiconductor laser based on the binary stratified structure is included.Type: GrantFiled: November 29, 1994Date of Patent: August 27, 1996Assignee: Lucent Technologies Inc.Inventors: Howard Z. Chen, Alfred Y. Cho
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Patent number: 5509025Abstract: This application discloses, to the best of our knowledge, the first unipolar laser. An exemplary embodiment of the laser was implemented in the GaInAs/AlInAs system and emits radiation of about 4.2 .mu.m wavelength. Embodiments in other material systems are possible, and the lasers can be readily designed to emit at a predetermined wavelength in a wide spectral region. We have designated the laser the "quantum cascade" (QC) laser. The QC laser comprises a multilayer semiconductor structure that comprises a multiplicity of essentially identical undoped "active" regions, a given active region being separated from an adjoining one by a doped "energy relaxation" region. In a currently preferred embodiment each active region comprises three coupled quantum wells designed to facilitate attainment of population inversion. In the currently preferred embodiment the energy relaxation regions are digitally graded gap regions. However, other energy relaxation regions are possible.Type: GrantFiled: January 9, 1995Date of Patent: April 16, 1996Assignee: AT&T Corp.Inventors: Federico Capasso, Alfred Y. Cho, Jerome Faist, Albert L. Hutchinson, Carlo Sirtori, Deborah L. Sivco
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Patent number: 5502787Abstract: Articles according to the invention include a semiconductor waveguide having a core and a cladding, with the cladding including doped semiconductor material. The doping level is selected such that both the real part n and the imaginary part k of the complex refractive index of the doped material are relatively low, exemplarily n<0.5 .epsilon..sub..infin..sup.1/2 and k<1, where .epsilon..sub..infin. is the high frequency lattice dielectric constant of the material. Appropriate choice of the doping level can result in improved confinement of the guided radiation without undue increase in the attenuation of the guided radiation. The invention exemplarily is embodied in a long wavelength (.about.8.5 .mu.m) quantum cascade laser. Other embodiments are contemplated.Type: GrantFiled: May 22, 1995Date of Patent: March 26, 1996Assignee: AT&T Corp.Inventors: Federico Capasso, Alfred Y. Cho, Jerome Faist, Albert L. Hutchinson, Carlo Sirtori, Deborah L. Sivco
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Patent number: 5457709Abstract: This application discloses, to the best of our knowledge, the first unipolar laser. An exemplary embodiment of the laser was implemented in the GaInAs/AlInAs system and emits radiation of about 4.2 .mu.m wavelength. Embodiments in other material systems are possible, and the lasers can be readily designed to emit at a predetermined wavelength in a wide spectral region. We have designated the laser the "quantum cascade" (QC) laser. The QC laser comprises a multilayer semiconductor structure that comprises a multiplicity of essentially identical undoper "active" regions, a given active region being separated from an adjoining one by a doped "energy relaxation" region. In a currently preferred embodiment each active region comprises three coupled quantum wells designed to facilitate attainment of population inversion. In the currently preferred embodiment the energy relaxation regions are digitally graded gap regions. However, other energy relaxation regions are possible.Type: GrantFiled: April 4, 1994Date of Patent: October 10, 1995Assignee: AT&T IPM Corp.Inventors: Federico Capasso, Alfred Y. Cho, Jerome Faist, Albert L. Hutchinson, Serge Luryi, Carlo Sirtori, Deborah L. Sivco
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Patent number: 5332690Abstract: This invention embodies an integrated optical package including an optical component having an asymmetric modal output, and a lens integrated with the component for coupling to another optical component having a large modal area. The coupling is achieved by the use of a Polymeric Elongated Waveguide Emulating (PEWE) lens. In the exemplary embodiment the first optical component is a modulator, and the other optical component is an optical fiber. A facet of the modulator is etched by reactive ion etching (REE) which allows integration of the PEWE lens on a common substrate. The lens is manufactured using a polymer film on a dielectric cladding layer. The fabrication relies on the remelt and reflow properties of polymer films to provide a smooth adiabatic mode contraction from a circular (optical fiber) mode (.apprxeq.6 .mu.m in diameter) to a semiconductor mode (.apprxeq.1 .mu.m) over a length of 250 .mu.m. The PEWE lens permits coupling with an insertion loss of 0.Type: GrantFiled: August 17, 1993Date of Patent: July 26, 1994Assignee: AT&T Bell LaboratoriesInventors: Alfred Y. Cho, Deborah L. Sivco, Daryoosh Vakhshoori
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Patent number: 5314838Abstract: Disclosed is a method for manufacturing a vertical cavity, surface-emitting laser. The method includes growing a distributed Bragg reflector having at least 10 layers of alternating composition on a gallium arsenide substrate. The growth surface of the substrate is tilted by an angle of 1.degree.-7.degree. from the orientation of a (100) surface toward the orientation of a (111)A surface. This results in improved reflectivity of the DBR.Type: GrantFiled: September 10, 1992Date of Patent: May 24, 1994Assignee: AT&T Bell LaboratoriesInventors: Alfred Y. Cho, Sung-Nee G. Chu, Kuochou Tai, Yeong-Her Wang
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Patent number: 5311009Abstract: In accordance with the invention, a quantum well device provides localized states for electrons having an energy E greater than the barrier height of the constituent quantum wells. The device comprises a confinement quantum well of width L.sub.w equal to an integer number n of deBroglie half wavelengths ##EQU1## and a plurality of adjacent quarter wavelength barriers and wells, each having a thickness equal to an odd number m of deBroglie quarter wavelengths. Constructive interference between the waves partially reflected by the interfaces between adjacent .lambda./4 barriers and .lambda./4 wells leads to the formation of a localized electron state at an energy E in the region of the confinement well. The device can be used in detectors and modulators employing transitions between a bound state within the well and the localized state above the well.Type: GrantFiled: July 31, 1992Date of Patent: May 10, 1994Assignee: AT&T Bell LaboratoriesInventors: Federico Capasso, Alfred Y. Cho, Jerome Faist, Carlo Sirtori, Deborah L. Sivco
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Patent number: 5265177Abstract: This invention embodies an integrated optical package including an optical component having an asymmetric modal output, and a lens integrated with the component for coupling to another optical component having a large modal area. The coupling is achieved by the use of a Polymeric Elongated Waveguide Emulating (PEWE) lens. In the exemplary embodiment the first optical component is a modulator, and the other optical component is an optical fiber. A facet of the modulator is etched by reactive ion etching (RIE) which allows integration of the PEWE lens on a common substrate. The lens is manufactured using a polymer film on a dielectric cladding layer. The fabrication relies on the remelt and reflow properties of polymer films to provide a smooth adiabatic mode contraction from a circular (optical fiber) mode (.apprxeq.6 .mu.m in diameter) to a semiconductor mode (.apprxeq.1 .mu.m) over a length of 250 .mu.m. The PEWE lens permits coupling with an insertion loss of 0.Type: GrantFiled: May 8, 1992Date of Patent: November 23, 1993Assignee: AT&T Bell LaboratoriesInventors: Alfred Y. Cho, Deborah L. Sivco, Daryoosh Vakhshoori
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Patent number: 5226053Abstract: This invention embodies a LED in which an optical cavity of the LED, which includes an active layer (or region) and confining layers, is within a resonant Fabry-Perot cavity. The LED with the resonant cavity, hereinafter called Resonant Cavity LED or RCLED, has a higher spectral purity and higher light emission intensity relative to conventional LEDs. The Fabry-Perot cavity is formed by a highly reflective multilayer distributed Bragg reflector (DBR) mirror (R.sub.B .gtoreq.0.99) and a mirror with a low to moderate reflectivity (R.sub.T .perspectiveto.0.25-0.99). The DBR mirror, placed in the RCLED structure between the substrate and the confining bottom layer, is used as a bottom mirror. Presence of the less reflective top mirror above the active region leads to an unexpected improvement in directional light emission characteristics.Type: GrantFiled: December 27, 1991Date of Patent: July 6, 1993Assignee: AT&T Bell LaboratoriesInventors: Alfred Y. Cho, Erdmann F. Schubert, Li-Wei Tu, George J. Zydzik
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Patent number: 5212395Abstract: This invention pertains to a p-i-n In.sub.0.53 Ga.sub.0.47 As photodiode having an optically transparent composite top electrode consisting of a thin semitransparent metal layer from 10 to 40 nm thick and a transparent cadmium tin oxide (CTO) layer from 90 to 600 nm thick. The metal layer makes a non-alloyed ohmic contact to the semiconductor surface, acts as a barrier between the semiconductor and the CTO preventing oxidation of the semiconductor from the O.sub.2 in the plasma during reactive magnetron sputtering of the CTO layer, and prevents formation of a p-n junction between the semiconductor and CTO. The CTO functions as the n or p contact, an optical window and an anti-reflection coating. The top electrode also avoids shadowing of the active layer by the top electrode, thus allowing greater collection of incident light. Since the top electrode is non-alloyed, inter-diffusion into the i-region is not relevant, which avoids an increased dark current.Type: GrantFiled: March 2, 1992Date of Patent: May 18, 1993Assignee: AT&T Bell LaboratoriesInventors: Paul R. Berger, Alfred Y. Cho, Niloy K. Dutta, John Lopata, Henry M. O'Bryan, Jr., Deborah L. Sivco, George J. Zydzik
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Patent number: 4999697Abstract: A plurality of decoupled quantum wells in a transistor device enables such device to operate with multiple-peak characteristics. The device is suitable for a variety of circuit applications in switching systems and in central processor logic units and memories; specific applications include frequency multipliers, waveform scramblers, parity-bit generators, analog-to digital converters, and multiple-valued logic units.Type: GrantFiled: September 14, 1988Date of Patent: March 12, 1991Assignee: AT&T Bell LaboratoriesInventors: Federico Capasso, Alfred Y. Cho, Susanta Sen
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Patent number: 4902912Abstract: A semiconductor integrated resonant-tunneling device having multiple negative-resistance regions, and having essentially equal current peaks in such regions, is useful as a highly compact element, e.g., in apparatus designed for ternary logic operations, frequency multiplication, waveform scrambling, memory operation, parity-bit generation, and coaxial-line driving. The device can be made by layer deposition on a substrate and includes a resonant-tunneling structure between contacts such that side-by-side first and third contacts are on one side, and a second contact is on the opposite side of the resonant-tunneling structure.Type: GrantFiled: June 13, 1989Date of Patent: February 20, 1990Assignee: American Telephone and Telegraph Company, AT&T Bell LaboratoriesInventors: Federico Capasso, Alfred Y. Cho, Susanta Sen, Masakazu Shoji, Deborah Sivco
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Patent number: 4853753Abstract: A semiconductor integrated resonant-tunneling device having multiple negative-resistance regions, and having essentially equal current peaks in such regions, is useful as a highly compact element, e.g., in apparatus designed for ternary logic operations, frequency multiplication, waveform scrambling, memory operation, parity-bit generation, and coaxial-line driving. The device can be made by layer deposition on a substrate and includes a resonant-tunneling structure between contacts such that side-by-side first and third contacts are on one side, and a second contact is on the opposite side of the resonant-tunneling structure. Disclosed further are (two-terminal) resonant-tunneling diodes as incorporated in memory devices, e.g., in lieu of 2-transistsor flip-flops; room-temperature device operation; and devices comprising an essentially undoped accelerator region between an emitter contact and a resonant-tunneling structure.Type: GrantFiled: November 5, 1987Date of Patent: August 1, 1989Assignee: American Telephone and Telegraph Company, AT&T Bell LaboratoriesInventors: Federico Capasso, Alfred Y. Cho, Susanta Sen
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Patent number: 4755860Abstract: An avalanche photodetector using a quantum well superlattice in which impact ionization of carriers in the well layers occurs across the band-edge discontinuity is described.Type: GrantFiled: August 5, 1986Date of Patent: July 5, 1988Assignee: American Telephone and Telegraph Company, AT&T Bell LaboratoriesInventors: Jeremy Allam, Federico Capasso, Alfred Y. Cho
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Patent number: 4750025Abstract: We have found that transistors have desirable device characteristics when the base region is composed of a lightly doped layer near the emitter junction and a heavily doped layer near the collector junction. The edge of the depletion region at the emitter-base junction is designed to stop in the lightly doped base region.Type: GrantFiled: January 30, 1986Date of Patent: June 7, 1988Assignee: American Telephone and Telegraph Company, AT&T Bell LaboratoriesInventors: Chung Y. Chen, Alfred Y. Cho
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Patent number: 4745447Abstract: Useful field effect transistors can be made with gallium indium arsenide as the electron conducting layer (channel layer) by incorporating a layer of gallium arsenide for the Schottky barrier. Relatively thick gallium arsenide layers are used to achieve low reverse leakage currents.Type: GrantFiled: June 14, 1985Date of Patent: May 17, 1988Assignee: American Telephone and Telegraph Company, AT&T Bell LaboratoriesInventors: Chung Y. Chen, Alfred Y. Cho, Sung-Nee G. Chu
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Patent number: 4739385Abstract: A modulation-doped field effect photodetector has a fast response time.Type: GrantFiled: January 12, 1987Date of Patent: April 19, 1988Assignee: American Telephone and Telegraph Company, AT&T Bell LaboratoriesInventors: Clyde G. Bethea, Chung Y. Chen, Alfred Y. Cho