Patents Represented by Attorney, Agent or Law Firm John P. Hohimer
  • Patent number: 5568499
    Abstract: A compound-semiconductor optical device and method. The optical device is provided with one or more asymmetrically-graded heterojunctions between compound semiconductor layers for forming a distributed Bragg reflector mirror having an improved electrical and thermal resistance. Efficient light-emitting devices such as light-emitting diodes, resonant-cavity light-emitting diodes, and vertical-cavity surface-emitting lasers may be formed according to the present invention, which may be applied to the formation of resonant-cavity photodetectors.
    Type: Grant
    Filed: April 7, 1995
    Date of Patent: October 22, 1996
    Assignee: Sandia Corporation
    Inventor: Kevin L. Lear
  • Patent number: 5557627
    Abstract: A visible semiconductor laser. The visible semiconductor laser includes an InAlGaP active region surrounded by one or more AlGaAs layers on each side, with carbon as the sole p-type dopant. Embodiments of the invention are provided as vertical-cavity surface-emitting lasers (VCSELs) and as edge-emitting lasers (EELs). One or more transition layers comprised of a substantially indium-free semiconductor alloy such as AlAsP, AlGaAsP, or the like may be provided between the InAlGaP active region and the AlGaAS DBR mirrors or confinement layers to improve carrier injection and device efficiency by reducing any band offsets. Visible VCSEL devices fabricated according to the invention with a one-wavelength-thick (1.lambda.) optical cavity operate continuous-wave (cw) with lasing output powers up to 8 mW, and a peak power conversion efficiency of up to 11%.
    Type: Grant
    Filed: May 19, 1995
    Date of Patent: September 17, 1996
    Assignee: Sandia Corporation
    Inventors: Richard P. Schneider, Jr., Mary H. Crawford
  • Patent number: 5523694
    Abstract: A scanning electron microscope apparatus and method are described for detecting and imaging open-circuit defects in an integrated circuit (IC). The invention uses a low-energy high-current focused electron beam that is scanned over a device surface of the IC to generate a charge-induced voltage alteration (CIVA) signal at the location of any open-circuit defects. The low-energy CIVA signal may be used to generate an image of the IC showing the location of any open-circuit defects. A low electron beam energy is used to prevent electrical breakdown in any passivation layers in the IC and to minimize radiation damage to the IC. The invention has uses for IC failure analysis, for production-line inspection of ICs, and for qualification of ICs.
    Type: Grant
    Filed: April 8, 1994
    Date of Patent: June 4, 1996
    Inventor: Edward I. Cole, Jr.
  • Patent number: 5493577
    Abstract: A semiconductor light-emitting device and method. The semiconductor light-emitting device is provided with at least one control layer or control region which includes an annular oxidized portion thereof to channel an injection current into the active region, and to provide a lateral refractive index profile for index guiding the light generated within the device. A periodic composition grading of at least one of the mirror stacks in the device provides a reduced operating voltage of the device. The semiconductor light-emitting device has a high efficiency for light generation, and may be formed either as a resonant-cavity light-emitting diode (RCLED) or as a vertical-cavity surface-emitting laser (VCSEL).
    Type: Grant
    Filed: December 21, 1994
    Date of Patent: February 20, 1996
    Assignee: Sandia Corporation
    Inventors: Kent D. Choquette, Kevin L. Lear, Richard P. Schneider, Jr.
  • Patent number: 5463649
    Abstract: A monolithically integrated photonic circuit combining a semiconductor source of excitation light with an optically active waveguide formed on the substrate. The optically active waveguide is preferably formed of a spin-on glass to which are added optically active materials which can enable lasing action, optical amplification, optical loss, or frequency conversion in the waveguide, depending upon the added material.
    Type: Grant
    Filed: August 6, 1993
    Date of Patent: October 31, 1995
    Assignee: Sandia Corporation
    Inventors: Carol I. H. Ashby, John P. Hohimer, Daniel R. Neal, G. Allen Vawter
  • Patent number: 5430305
    Abstract: An apparatus and method are described for analyzing an integrated circuit (IC), The invention uses a focused light beam that is scanned over a surface of the IC to generate a light-induced voltage alteration (LIVA) signal for analysis of the IC, The LIVA signal may be used to generate an image of the IC showing the location of any defects in the IC; and it may be further used to image and control the logic states of the IC. The invention has uses for IC failure analysis, for the development of ICs, for production-line inspection of ICs, and for qualification of ICs.
    Type: Grant
    Filed: April 8, 1994
    Date of Patent: July 4, 1995
    Assignee: The United States of America as represented by the United States Department of Energy
    Inventors: Edward I. Cole, Jr., Jerry M. Soden