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).

  • Patent number: 5381434
    Abstract: A semiconductor diode laser comprising an active layer (12) having multiple compressively strained quantum wells (54) of AlGaInAs sandwiched between barriers (52) of AlGaInAs lattice-matched to InP and of a precisely defined bandgap dependent on the composition of the quantum wells. The active layer is surrounded by oppositely doped cladding layers (48, 50, 52, 58, 60) so as to form an optical waveguide. The laser very efficiently emits 1.3-.mu.m light, particularly at high operating temperatures.
    Type: Grant
    Filed: March 30, 1993
    Date of Patent: January 10, 1995
    Assignee: Bell Communications Research, Inc.
    Inventors: Rajaram Bhat, Chung-en Zah
  • Patent number: 5323416
    Abstract: A semiconductor interference mirror principally comprising a large number of pairs (36) of semiconductor layers (38,40) having different dielectric constants and having optical thicknesses equal to one-quarter of the wavelength of light to be reflected. For example, the two semiconductors are InP and InGaAsP for reflecting 1.55-.mu.m light. However, every 10 to 15 periods in the mirror, the InP layer (44) is grown more slowly to a thickness that is an odd multiple of its usual quarter-wavelength thickness. Because indium is so mobile and binary composition is well defined, the binary InP layer replanarizes the growth, thus assuring a planar mirror. The faster growth rate for the majority of the mirror allows the mirror to be grown in a shorter time, thus reducing process variations.
    Type: Grant
    Filed: August 20, 1993
    Date of Patent: June 21, 1994
    Assignee: Bell Communications Research, Inc.
    Inventors: Rajaram Bhat, Sung-Joo Yoo
  • Patent number: 5302847
    Abstract: A III-V semiconductor heterojunction in which a capping layer (14) is formed between the two layers (10, 16) of the heterojunction to prevent any deleterious effects due to As-P exchange. When InAlAs is grown on InP, the capping layer is AlP. When GaAs is grown on GaInP, the capping layer is GaP.
    Type: Grant
    Filed: June 4, 1993
    Date of Patent: April 12, 1994
    Assignee: Bell Communications Research, Inc.
    Inventors: Rajaram Bhat, Maria J. S. P. Brasil, Robert E. Nahory, William E. Quinn, Maria C. Tamargo
  • Patent number: 5288327
    Abstract: A reactor cell for use in organo-metallic chemical vapor deposition (OMCVD). Multiple precursor gases are combined in a supply tube (14). A deflector section (56) connected to the supply tube consists of three tubes (58, 60, 61) joined at right angles to each other and to the supply tube in order to maximize the turbulence in the gas flow and to thereby uniformly mix the gas. The last of the three tubes is perpendicularly joined to a tapered section (30) of rectangular cross-section that tapers outwardly toward a deposition chamber (22) of rectangular cross section containing a heated susceptor (18) holding the wafer (20) over which the uniformly mixed gas flows and cracks, thereby epitaxially depositing some of its constituents on the wafer.
    Type: Grant
    Filed: August 18, 1993
    Date of Patent: February 22, 1994
    Assignee: Bell Communications Research, Inc.
    Inventor: Rajaram Bhat
  • Patent number: 5246878
    Abstract: A III-V semiconductor heterojunction in which a capping layer (14) is formed between the two layers (10, 16) of the heterojunction to prevent any deleterious effects due to As--P exchange. When InAlAs is grown on InP, the capping layer is AlP. When GaAs is grown on GaInP, the capping layer is GaP.
    Type: Grant
    Filed: March 27, 1992
    Date of Patent: September 21, 1993
    Assignee: Bell Communications Research, Inc.
    Inventors: Rajaram Bhat, Maria J. S. P. Brasil, Robert E. Nahory, William E. Quinn, Maria C. Tamargo
  • Patent number: 5226383
    Abstract: A gas foil susceptor for rotating a wafer (16) during growth in a chemical vapor deposition chamber. Inner and outer annular grooves (24, 26) are formed at the bottom of a tapered depression (14) in the upper surface of a base (10). Feed and discharge tubes (28, 32) extend laterally from the annular grooves to the exterior (34) of the base. A disk (12) is fit within the depression and bears the wafer (16) on its upper surface. Three spiral channels (38, 40, 42) are formed on the bottom of the disk and their inner and outer ends (44, 46) overlie the inner and outer circular channels respectively. A gas flow is set up between the two circular channels and impinges the sides of the spiral channels to thereby rotate the disk and the wafer on it. When the base and disk are made of graphite, an external RF coil can controllably heat the wafer.
    Type: Grant
    Filed: November 9, 1992
    Date of Patent: July 13, 1993
    Assignee: Bell Communications Research, Inc.
    Inventor: Rajaram Bhat
  • Patent number: 5207864
    Abstract: A method of fusing together wafers (10, 30) or other semiconductor bodies comprising different semiconductors. In the case that wafers of InP and GaAs or other compound semiconductors are to be bonded, the wafers are cleaned with etchant, and their surfaces are placed together. While the wafers are forced together under moderate pressure and clean hydrogen flows over the wafers, the temperature is raised to 650.degree. C., close to the deposition temperature for epitaxial InP, and maintained for 30 minutes. In the case that one of the wafers is silicon (FIG. 5), both wafers are assembled together in hydrofluoric acid, in which the two wafers bond together by van der Waals force. Then, the assembly is placed in a furnace and annealed at 650.degree. C. A sharp hetero-interface (32, 66, 70) is produced with only surface defects which do not propagate into the bulk. Either wafer may be preformed with a multi-layer opto-electronic structure (12).
    Type: Grant
    Filed: December 30, 1991
    Date of Patent: May 4, 1993
    Assignee: Bell Communications Research
    Inventors: Rajaram Bhat, Yu-hwa Lo
  • Patent number: 5065200
    Abstract: The method and product of laterally defining semiconductor structures using geometry depending doping. A compound semiconductor substrate, for example, InP or GaAs, is formed with a groove in a predetermined direction. One or more epitaxial layers are deposited on both the grooved portion and the planar portions of the substrate and include both n-type and p-type dopants. The incorporation rates of the dopants into the deposited layers depend upon the crystalline orientation of the planar surface or the sidewalls of the groove. Thereby, the planar portion may be formed of one conductivity type and the groove with the other. The invention is particularly useful for defining the current structure in a semiconductor laser.
    Type: Grant
    Filed: December 21, 1989
    Date of Patent: November 12, 1991
    Assignee: Bell Communications Research, Inc.
    Inventors: Rajaram Bhat, Chung-en Zah
  • Patent number: 4931132
    Abstract: A method and apparatus for epitaxial growth of precisely one monolayer. The growth is by organometallic chemical vapor deposition in which the substrate is alternately exposed to the anion and cation of a III-V compound. During deposition of the cation, for instance Ga or Al, reflectance difference spectroscopy is performed to obtain the difference of reflected light beams polarized in orthogonal directions. A growth of a monolayer and even of a partial monolayer can be monitored in real time.
    Type: Grant
    Filed: October 7, 1988
    Date of Patent: June 5, 1990
    Assignee: Bell Communications Research, Inc.
    Inventors: David E. Aspnes, Rajaram Bhat, Etienne G. Colas, Leigh T. Florez, James P. Harbison, Amabrose A. Studna