Patents by Inventor Sarath D. Gunapala

Sarath D. Gunapala 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).

  • Patent number: 9831372
    Abstract: Barrier infrared detectors configured to operate in the long-wave (LW) infrared regime are provided. The barrier infrared detector systems may be configured as pin, pbp, barrier and double heterostructrure infrared detectors incorporating optimized p-doped absorbers capable of taking advantage of high mobility (electron) minority carriers. The absorber may be a p-doped Ga-free InAs/InAsSb material. The p-doping may be accomplished by optimizing the Be doping levels used in the absorber material. The barrier infrared detectors may incorporate individual superlattice layers having narrower periodicity and optimization of Sb composition to achieve cutoff wavelengths of ˜10 ?m.
    Type: Grant
    Filed: May 13, 2016
    Date of Patent: November 28, 2017
    Assignee: California Institute of Technology
    Inventors: Arezou Khoshakhlagh, David Z. Ting, Sarath D. Gunapala
  • Patent number: 9647164
    Abstract: Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.
    Type: Grant
    Filed: October 16, 2014
    Date of Patent: May 9, 2017
    Assignee: California Institute of Technology
    Inventors: David Z. Ting, Sarath D. Gunapala, Alexander Soibel, Jean Nguyen, Arezou Khoshakhlagh
  • Publication number: 20160336476
    Abstract: Barrier infrared detectors configured to operate in the long-wave (LW) infrared regime are provided. The barrier infrared detector systems may be configured as pin, pbp, barrier and double heterostructrure infrared detectors incorporating optimized p-doped absorbers capable of taking advantage of high mobility (electron) minority carriers. The absorber may be a p-doped Ga-free InAs/InAsSb material. The p-doping may be accomplished by optimizing the Be doping levels used in the absorber material. The barrier infrared detectors may incorporate individual superlattice layers having narrower periodicity and optimization of Sb composition to achieve cutoff wavelengths of ˜10 ?m.
    Type: Application
    Filed: May 13, 2016
    Publication date: November 17, 2016
    Inventors: Arezou Khoshakhlagh, David Z. Ting, Sarath D. Gunapala
  • Patent number: 9466741
    Abstract: In order to increase the spectral response range and improve the mobility of the photo-generated carriers (e.g. in an nBn photodetector), a digital alloy absorber may be employed by embedding one (or fraction thereof) to several monolayers of a semiconductor material (insert layers) periodically into a different host semiconductor material of the absorber layer. The semiconductor material of the insert layer and the host semiconductor materials may have lattice constants that are substantially mismatched. For example, this may performed by periodically embedding monolayers of InSb into an InAsSb host as the absorption region to extend the cutoff wavelength of InAsSb photodetectors, such as InAsSb based nBn devices. The described technique allows for simultaneous control of alloy composition and net strain, which are both key parameters for the photodetector operation.
    Type: Grant
    Filed: December 16, 2009
    Date of Patent: October 11, 2016
    Assignee: California Institute of Technology
    Inventors: Cory J. Hill, David Z. Ting, Sarath D. Gunapala
  • Patent number: 9214581
    Abstract: Systems and methods of implementing barrier infrared detectors on lattice mismatched substrates are provided. The barrier infrared detector systems combine an active detector structure (e.g., contact/barrier/absorber pairs) with a non-lattice matched substrate through a multi-layered transitional structure that forms a virtual substrate that can be strain balanced with the detector structure. The transitional metamorphic layer may include one or both of at least one graded metamorphic buffer layer or interfacial misfit array (IMF). A further interfacial layer may be interposed within the transitional structure, in some embodiments this interfacial layer includes at least one layer of AlSb.
    Type: Grant
    Filed: February 11, 2014
    Date of Patent: December 15, 2015
    Assignee: CALIFORNIA INSTITUTE OF TECHNOLOGY
    Inventors: Arezou Khoshakhlagh, David Z Ting, Sarath D. Gunapala, Cory J. Hill
  • Publication number: 20150145091
    Abstract: Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.
    Type: Application
    Filed: October 16, 2014
    Publication date: May 28, 2015
    Inventors: David Z. Ting, Sarath D. Gunapala, Alexander Soibel, Jean Nguyen, Arezou Khoshakhlagh
  • Patent number: 8928036
    Abstract: A barrier infrared detector with absorber materials having selectable cutoff wavelengths and its method of manufacture is described. A GaInAsSb absorber layer may be grown on a GaSb substrate layer formed by mixing GaSb and InAsSb by an absorber mixing ratio. A GaAlAsSb barrier layer may then be grown on the barrier layer formed by mixing GaSb and AlSbAs by a barrier mixing ratio. The absorber mixing ratio may be selected to adjust a band gap of the absorber layer and thereby determine a cutoff wavelength for the barrier infrared detector. The absorber mixing ratio may vary along an absorber layer growth direction. Various contact layer architectures may be used. In addition, a top contact layer may be isolated into an array of elements electrically isolated as individual functional detectors that may be used in a detector array, imaging array, or focal plane array.
    Type: Grant
    Filed: September 25, 2009
    Date of Patent: January 6, 2015
    Assignee: California Institute of Technology
    Inventors: David Z. Ting, Cory J. Hill, Alexander Seibel, Sumith Y. Bandara, Sarath D. Gunapala
  • Patent number: 8928029
    Abstract: Bias-switchable dual-band infrared detectors and methods of manufacturing such detectors are provided. The infrared detectors are based on a back-to-back heterojunction diode design, where the detector structure consists of, sequentially, a top contact layer, a unipolar hole barrier layer, an absorber layer, a unipolar electron barrier, a second absorber, a second unipolar hole barrier, and a bottom contact layer. In addition, by substantially reducing the width of one of the absorber layers, a single-band infrared detector can also be formed.
    Type: Grant
    Filed: December 12, 2012
    Date of Patent: January 6, 2015
    Assignee: California Institute of Technology
    Inventors: David Z. Ting, Sarath D. Gunapala, Alexander Soibel, Jean Nguyen, Arezou Khoshakhlagh
  • Publication number: 20140225064
    Abstract: Systems and methods of implementing barrier infrared detectors on lattice mismatched substrates are provided. The barrier infrared detector systems combine an active detector structure (e.g., contact/barrier/absorber pairs) with a non-lattice matched substrate through a multi-layered transitional structure that forms a virtual substrate that can be strain balanced with the detector structure. The transitional metamorphic layer may include one or both of at least one graded metamorphic buffer layer or interfacial misfit array (IMF). A further interfacial layer may be interposed within the transitional structure, in some embodiments this interfacial layer includes at least one layer of AlSb.
    Type: Application
    Filed: February 11, 2014
    Publication date: August 14, 2014
    Applicant: California Institute of Technology
    Inventors: Arezou Khoshakhlagh, David Z. Ting, Sarath D. Gunapala, Cory J. Hill
  • Patent number: 8600483
    Abstract: Described is a mobile in vivo infrared brain scan and analysis system. The system includes a data collection subsystem and a data analysis subsystem. The data collection subsystem is a helmet with a plurality of infrared (IR) thermometer probes. Each of the IR thermometer probes includes an IR photodetector capable of detecting IR radiation generated by evoked potentials within a user's skull. The helmet is formed to collect brain data that is reflective of firing neurons in a mobile subject and transmit the brain data to the data analysis subsystem. The data analysis subsystem is configured to generate and display a three-dimensional image that depicts a location of the firing neurons. The data analysis subsystem is also configured to compare the brain data against a library of brain data to detect an anomaly in the brain data, and notify a user of any detected anomaly in the brain data.
    Type: Grant
    Filed: June 18, 2008
    Date of Patent: December 3, 2013
    Assignee: California Institute of Technology
    Inventors: Frederick W. Mintz, Philip I. Moynihan, Sarath D. Gunapala
  • Patent number: 8368051
    Abstract: An infrared detector having a hole barrier region adjacent to one side of an absorber region, an electron barrier region adjacent to the other side of the absorber region, and a semiconductor adjacent to the electron barrier.
    Type: Grant
    Filed: July 10, 2009
    Date of Patent: February 5, 2013
    Assignee: California Institute of Technology
    Inventors: David Z. Ting, Sumith V. Bandara, Cory J. Hill, Sarath D. Gunapala
  • Patent number: 8217480
    Abstract: A superlattice-based infrared absorber and the matching electron-blocking and hole-blocking unipolar barriers, absorbers and barriers with graded band gaps, high-performance infrared detectors, and methods of manufacturing such devices are provided herein. The infrared absorber material is made from a superlattice (periodic structure) where each period consists of two or more layers of InAs, InSb, InSbAs, or InGaAs. The layer widths and alloy compositions are chosen to yield the desired energy band gap, absorption strength, and strain balance for the particular application. Furthermore, the periodicity of the superlattice can be “chirped” (varied) to create a material with a graded or varying energy band gap.
    Type: Grant
    Filed: August 3, 2011
    Date of Patent: July 10, 2012
    Assignee: California Institute of Technology
    Inventors: David Z. Ting, Arezou Khoshakhlagh, Alexander Soibel, Cory J. Hill, Sarath D. Gunapala
  • Publication number: 20120145996
    Abstract: A superlattice-based infrared absorber and the matching electron-blocking and hole-blocking unipolar barriers, absorbers and barriers with graded band gaps, high-performance infrared detectors, and methods of manufacturing such devices are provided herein. The infrared absorber material is made from a superlattice (periodic structure) where each period consists of two or more layers of InAs, InSb, InSbAs, or InGaAs. The layer widths and alloy compositions are chosen to yield the desired energy band gap, absorption strength, and strain balance for the particular application. Furthermore, the periodicity of the superlattice can be “chirped” (varied) to create a material with a graded or varying energy band gap.
    Type: Application
    Filed: August 3, 2011
    Publication date: June 14, 2012
    Applicant: California Institute of Technology
    Inventors: David Z. Ting, Arezou Khoshakhlagh, Alexander Soibel, Cory J. Hill, Sarath D. Gunapala
  • Publication number: 20110176577
    Abstract: A multi-waveband temperature sensor array, in which each superpixel (e.g., 2×2 pixel cell) operates at a distinct thermal infrared (IR) waveband (e.g. four wavebands) is disclosed. Using an example high spatial resolution, four-band thermal IR band photodetector array, accurate temperature measurements on the surface of an object can be made without prior knowledge of the object emissivity. The multiband photodetector may employ intersubband transition in III-V semiconductor-based quantum layered structures where each photodetector stack absorbs photons within the specified wavelength band while allowing the transmission of photons in other spectral bands, thus efficiently permitting multiband detection. This produces multiple, spectrally resolved images of a scene that are recorded simultaneously in a single snapshot of the FPA. From the multispectral images and calibration information about the system, computational algorithms are used to produce the surface temperature map of a target.
    Type: Application
    Filed: December 8, 2009
    Publication date: July 21, 2011
    Applicant: California Institute of Technology
    Inventors: Sumith V. Bandara, Sarath D. Gunapala, John K. Liu, Robert C. Stirbl, Daniel W. Wilson, David Z. Ting
  • Publication number: 20100155777
    Abstract: In order to increase the spectral response range and improve the mobility of the photo-generated carriers (e.g. in an nBn photodetector), a digital alloy absorber may be employed by embedding one (or fraction thereof) to several monolayers of a semiconductor material (insert layers) periodically into a different host semiconductor material of the absorber layer. The semiconductor material of the insert layer and the host semiconductor materials may have lattice constants that are substantially mismatched. For example, this may performed by periodically embedding monolayers of InSb into an InAsSb host as the absorption region to extend the cutoff wavelength of InAsSb photodetectors, such as InAsSb based nBn devices. The described technique allows for simultaneous control of alloy composition and net strain, which are both key parameters for the photodetector operation.
    Type: Application
    Filed: December 16, 2009
    Publication date: June 24, 2010
    Applicant: California Institute of Technology
    Inventors: Cory J. Hill, David Z. Ting, Sarath D. Gunapala
  • Patent number: 7737411
    Abstract: An nBn detector is described where for some embodiments the barrier layer has a concentration gradient, for some embodiments the absorption layer has a concentration gradient, and for some embodiments the absorption layer is a chirped strained layer super lattice. The use of a graded barrier or absorption layer, or the use of a chirped strained layer super lattice for the absorption layer, allows for design of the energy bands so that the valence band may be aligned across the device. Other embodiments are described and claimed.
    Type: Grant
    Filed: October 10, 2008
    Date of Patent: June 15, 2010
    Assignee: California Institute of Technology
    Inventors: Sarath D. Gunapala, David Z. Ting, Cory J. Hill, Sumith V. Bandara
  • Publication number: 20100072514
    Abstract: A barrier infrared detector with absorber materials having selectable cutoff wavelengths and its method of manufacture is described. A GaInAsSb absorber layer may be grown on a GaSb substrate layer formed by mixing GaSb and InAsSb by an absorber mixing ratio. A GaAlAsSb barrier layer may then be grown on the barrier layer formed by mixing GaSb and AlSbAs by a barrier mixing ratio. The absorber mixing ratio may be selected to adjust a band gap of the absorber layer and thereby determine a cutoff wavelength for the barrier infrared detector. The absorber mixing ratio may vary along an absorber layer growth direction. Various contact layer architectures may be used. In addition, a top contact layer may be isolated into an array of elements electrically isolated as individual functional detectors that may be used in a detector array, imaging array, or focal plane array.
    Type: Application
    Filed: September 25, 2009
    Publication date: March 25, 2010
    Applicant: California Institute of Technology
    Inventors: David Z. Ting, Cory J. Hill, Alexander Soibel, Sumith V. Bandara, Sarath D. Gunapala
  • Publication number: 20100006822
    Abstract: An infrared detector having a hole barrier region adjacent to one side of an absorber region, an electron barrier region adjacent to the other side of the absorber region, and a semiconductor adjacent to the electron barrier.
    Type: Application
    Filed: July 10, 2009
    Publication date: January 14, 2010
    Applicant: California Institute of Technology
    Inventors: David Z. Ting, Sumith V. Bandara, Cory J. Hill, Sarath D. Gunapala
  • Patent number: 7599061
    Abstract: The present invention is directed to methods of photonic crystal formation, and to methods and apparatus for using such photonic crystals, particularly in conjunction with detector arrays. Photonic crystal parameters and detector array parameters are compared to optimize the selection and orientation of a photonic crystal shape. A photonic crystal is operatively positioned relative to a plurality of light sensors. The light sensors can be separated by a pitch distance and positioned within one half of the pitch distance of an exit surface of the photonic crystals.
    Type: Grant
    Filed: July 21, 2005
    Date of Patent: October 6, 2009
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventors: David Z. Ting, Cory J. Hill, Sumith V. Bandara, Sarath D. Gunapala
  • Publication number: 20090127462
    Abstract: An nBn detector is described where for some embodiments the barrier layer has a concentration gradient, for some embodiments the absorption layer has a concentration gradient, and for some embodiments the absorption layer is a chirped strained layer super lattice. The use of a graded barrier or absorption layer, or the use of a chirped strained layer super lattice for the absorption layer, allows for design of the energy bands so that the valence band may be aligned across the device. Other embodiments are described and claimed.
    Type: Application
    Filed: October 10, 2008
    Publication date: May 21, 2009
    Applicant: California Institute of Technology
    Inventors: Sarath D. Gunapala, David Z. Ting, Cory J. Hill, Sumith V. Bandara