Patents by Inventor Erdmann F. Schubert

Erdmann F. Schubert 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: 5550089
    Abstract: An optoelectronic lII-V or II-VI semiconductor device comprises a thin film coating with optical characteristics providing low midgap interface state density. A field effect device for inversion channel applications on III-V semiconductors also comprises a thin dielectric film providing required interface characteristics. The thin film is also applicable to passivation of states on exposed surfaces of electronic III-V devices. The thin film comprises a uniform, homogeneous, dense, stoichiometric gallium oxide (Ga.sub.2 O.sub.3) dielectric thin film, fabricated by electron-beam evaporation of a single crystal, high purity Gd.sub.3 Ga.sub.5 O.sub.12 complex compound on semiconductor substrates kept at temperatures ranging from 40.degree. to 370.degree. C. and at background pressures at or above 1.times.10.sup.-10 Torr.
    Type: Grant
    Filed: March 23, 1994
    Date of Patent: August 27, 1996
    Assignee: Lucent Technologies Inc.
    Inventors: Niloy K. Dutta, Russell J. Fischer, Neil E. J. Hunt, Matthias Passlack, Erdmann F. Schubert, George J. Zydzik
  • Patent number: 5451548
    Abstract: Disclosed is a method of fabricating a stoichiometric gallium oxide (Ga.sub.2 O.sub.3) thin film with dielectric properties on at least a portion of a semiconducting, insulating or metallic substrate. The method comprises electron-beam evaporation of single crystal, high purity Gd.sub.3 Ga.sub.5 O.sub.12 complex compound combining relatively ionic oxide, such as Gd.sub.2 O.sub.3, with the more covalent oxide Ga.sub.2 O.sub.3 such as to deposit a uniform, homogeneous, dense Ga.sub.2 O.sub.3 thin film with dielectric properties on a variety of said substrates, the semiconducting substrates including III-V and II-VI compound semiconductors.
    Type: Grant
    Filed: March 23, 1994
    Date of Patent: September 19, 1995
    Assignee: AT&T Corp.
    Inventors: Neil E. J. Hunt, Matthias Passlack, Erdmann F. Schubert, George J. Zydzik
  • Patent number: 5363398
    Abstract: Absorption properties of an optically active medium can be changed drastically by a Fabry-Perot microcavity. Optically active medium of the cavity includes a host material which is not optically active and at least one rare earth ion which provides optical activity to the medium. The Fabry-Perot cavity is designed to be resonant with excitation wavelength of an absorption band of the host material. The excitation is provided by a source of radiation positioned such that the radiation impinges on the cavity at an angle within a range of from zero to less than 90 degrees from the normal to the top surface of the cavity. In one embodiment Er-implanted SiO.sub.2 is used as the optically active medium. SiO.sub.2 :Er has an absorption band at 980 nm and an emission band at 1.55 .mu.m due to 4f intra-atomic transitions of Er.sup.3+ ions. The Fabry-Perot cavity is designed to be resonant with the 980 nm absorption band of SiO.sub.2 :Er.
    Type: Grant
    Filed: September 30, 1993
    Date of Patent: November 8, 1994
    Assignee: AT&T Bell Laboratories
    Inventors: Alastair M. Glass, Neil E. J. Hunt, John M. Poate, Erdmann F. Schubert, George J. Zydzik
  • Patent number: 5362977
    Abstract: This invention embodies single mirror light-emitting diodes (LEDs) with enhanced intensity. The LEDs are Group III-V and/or II-IV compound semiconductor structures with a single metallic mirror. The enhanced intensity is obtained by placing an active region of the LED having from two to ten, preferably from four to eight, quantum wells at an anti-node of the optical node of the device created by a nearby metallic mirror. Such multiquantum well LED structures exhibit enhanced efficiencies approaching that of a perfect isotropic emitter.
    Type: Grant
    Filed: December 28, 1992
    Date of Patent: November 8, 1994
    Assignee: AT&T Bell Laboratories
    Inventors: Neil E. J. Hunt, Erdmann F. Schubert
  • Patent number: 5315128
    Abstract: Described is a resonant-cavity p-i-n photodetector based on the reflection or transmission through a Fabry-Perot cavity incorporating non-epitaxial, amorphous layers with alternating refractive index difference which layers are electron-beam deposited on a light-gathering side of a commercially available photodetector. The materials of the Fabry-Perot cavity are selectable from materials, refractive indices of which fall within a large range (from n=1.26 for CaF.sub.2 to n=3.5 for Si) preferably from materials which are depositable in an amorphous state. The material combinations are selected so that only wavelengths resonant with the cavity mode will be detected. The microcavity of the RC-PIN design can also be deposited on any existing detector structure, without modification of semiconductor growth. Such a photodetector would be useful for wavelength de-multiplexing applications.
    Type: Grant
    Filed: April 30, 1993
    Date of Patent: May 24, 1994
    Assignee: AT&T Bell Laboratories
    Inventors: Neil E. J. Hunt, Erdmann F. Schubert, George J. Zydzik
  • Patent number: 5268582
    Abstract: This invention embodies p-n junction devices comprising Group III-V compound semiconductors in which the p or n or both p and n regions are formed by a superlattice selectively doped with an amphoteric Group IV element dopant selected from carbon, germanium and silicone. The superlattice includes a plurality of periods, each including two layers. Depending on the conductivity type, only one of the layers in the periods forming the superlattice region of said type of conductivity is selectively doped with said dopant, leaving the other layer in these periods undoped. The superlattice is formed by Molecular Beam Epitaxy technique, and the dopant is incorporated into respective layers by delta-doping as in a sheet centrally deposited between monolayers forming the respective layers of the period. Each period includes 5 to 15 monolayers deposited in the two layers in a numerical ratio corresponding to a cation compositional ratio in the compound semiconductor. Low growth temperatures, e.g. ranging from 410.
    Type: Grant
    Filed: June 24, 1992
    Date of Patent: December 7, 1993
    Assignee: AT&T Bell Laboratories
    Inventors: Rose F. Kopf, Erdmann F. Schubert
  • Patent number: 5249195
    Abstract: This invention embodies an optical device with a Fabry-Perot cavity formed by two reflective mirrors and an active layer which is doped with a rare earth element selected from lanthanide series elements with number 57 through 71. The thickness of the active layer being a whole number multiple of .lambda./2 wherein .lambda. is the operating, or emissive, wavelength of the device, said whole number being one of the numbers ranging from 1 to 5, the fundamental mode of the cavity being in resonance with the emission wavelength of said selected rare earth element. Cavity-quality factors exceeding Q=300 and finesses of 73 are achieved with structures consisting of two Si/SiO.sub.2 distributed Bragg reflector (DBR) mirrors and an Er-implanted (.lambda./2) SiO.sub.2 active region. The bottom DBR mirror consists of four pairs and the upper DBR mirror consists of two-and-a half pairs of quarterwave (.lambda./4) layers of Si and SiO.sub.2.
    Type: Grant
    Filed: June 30, 1992
    Date of Patent: September 28, 1993
    Assignee: AT&T Bell Laboratories
    Inventors: Leonard C. Feldman, Neil E. J. Hunt, Dale C. Jacobson, John M. Poate, Erdmann F. Schubert, Arjen M. Vredenberg, Yiu-Huen Wong, George J. Zydzik
  • Patent number: 5226055
    Abstract: It has been found that in the preparation of devices having repetitive layers, such as distributed Bragg reflectors, the dopant introduced during processing redistributes itself in a deleterious manner. In particular, this dopant through various effects segregates and diffuses from one layer into the interface region of the second layer. As a result, properties such as electrical resistance of the structure become unacceptably high. By utilizing various expedients such as carbon doping this segregation and its associated deleterious effects are avoided.
    Type: Grant
    Filed: September 30, 1991
    Date of Patent: July 6, 1993
    Assignee: AT&T Bell Laboratories
    Inventors: Stephen W. Downey, Adrian B. Emerson, Rose F. Kopf, Erdmann F. Schubert
  • Patent number: 5226053
    Abstract: 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: Grant
    Filed: December 27, 1991
    Date of Patent: July 6, 1993
    Assignee: AT&T Bell Laboratories
    Inventors: Alfred Y. Cho, Erdmann F. Schubert, Li-Wei Tu, George J. Zydzik
  • Patent number: 5206871
    Abstract: This invention embodies a Vertical Cavity Surface Emitting Laser with a top mirror comprising at least one pair of quarterwave layers, each pair consisting of a low index of refraction layer and a high index of refraction layer, the high index of refraction layer being a semiconductor chosen from GaP and ZnS and the low index of refraction layer being chosen from borosilicate glass (BSG) CaF.sub.2,MgF.sub.2 and NaF. Especially useful in vertical cavity surface emitting lasers are mirrors formed by a stack of a plurality of pairs of GaP/BSG or ZnS/CdF.sub.2. Such mirrors have a high reflectivity characteristics required for an efficient operation of the laser. The GaP/BSG or ZnS/CaF.sub.2 mirror structure represents a considerable improvement over previous designs for VCSELs in terms of ultimate reflectivity, low loss, and post growth processing compatibility.
    Type: Grant
    Filed: December 27, 1991
    Date of Patent: April 27, 1993
    Assignee: AT&T Bell Laboratories
    Inventors: Dennis G. Deppe, Niloy K. Dutta, Erdmann F. Schubert, Li-Wei Tu, George J. Zydzik
  • Patent number: 5170407
    Abstract: Conduction band or valence band discontinuities occurring at the junction of two unipolar heterogeneous semiconductors can be eliminated by compositional grading of the heterointerface and appropriate doping of the interfacial region. The compositional potential of graded junction and an interface dipole potential generated by modulation doping of the interfacial region are selected such that they exactly compensate each other. The compositional grading of the interface is achieved by semiparabolic grading of narrow regions immediately adjacent each side of the interface. The modulation doping is achieved by doping the two materials with suitable dopants, donors for the conductance band or acceptors for the valence band, depending on the polarity of the structure. This reduces the resistance in periodic semiconductor multilayer structures leading to low-resistance distributed Bragg reflectors.
    Type: Grant
    Filed: October 11, 1991
    Date of Patent: December 8, 1992
    Assignee: AT&T Bell Laboratories
    Inventors: Erdmann F. Schubert, Li-Wei Tu, George J. Zydzik
  • Patent number: 5115441
    Abstract: Optically transparent and electrically conductive cadmium tin oxide or indium tin oxide is employed in vertical cavity surface emitting lasers for vertical current injection. Continuous wave lasing at room temperature is achieved in GaAs/AlGaAs quantum well lasers. Devices with a 10 .mu.m optical window which also serves as a vertical current injection inlet give lasing threshold currents as low as 3.8 mA. The differential series resistance is (350-450) .OMEGA. with a diode voltage of (5.1-5.6) V at the lasing threshold. Far field pattern of the laser emission is Gaussian-like with a full width at half maximum of 7.degree..
    Type: Grant
    Filed: January 3, 1991
    Date of Patent: May 19, 1992
    Assignee: AT&T Bell Laboratories
    Inventors: Rose F. Kopf, Henry M. O'Bryan, Jr., Erdmann F. Schubert, Li-Wei Tu, Yeong-Her Wang, George J. Zydzik
  • Patent number: 5068868
    Abstract: This invention is a semiconductor vertical cavity surface emitting laser comprising a lasing cavity with an active layer, a bottom (rear) mirror and a top (front) mirror, and a front and rear electrodes for applying excitation current in direction substantially parallel to the direction of optical propagation. In accordance with this invention the front mirror comprises a thin, semitransparent metal layer which also acts as the front electrode. The metal layer is upon a highly doped layer forming a non-alloyed ohmic contact. The metal is selected from Ag and Al and is deposited in thickness ranging from 5 to 55 nm. The VCSEL is a semiconductor device wherein the semiconductor material is a III-V or II-VI compound semiconductor. For a VCSEL with GaAs active layer, the light output from the front metal mirror/electrode side yields a high external differential quantum efficiency as high as 54 percent. This is the highest quantum efficiency obtained in VCSEL structures.
    Type: Grant
    Filed: May 21, 1990
    Date of Patent: November 26, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Dennis G. Deppe, Leonard C. Feldman, Rose F. Kopf, Erdmann F. Schubert, Li Wei Tu, George J. Zydzik
  • Patent number: 5031012
    Abstract: The use of alternating n and p type regions asymmetrically spaced in a semiconductor material yields extremely advantageous properties. In particular, by controlling the doping level and the spatial configuration of the doped region both the device response and its optical properties are controllable. Therefore, in applications such as those involving optical switches LEDs, lasers and long wavelength detectors, both the speed of device and its optical properties are controllable. As a result, greater fabrication flexibility than previously available is possible.
    Type: Grant
    Filed: June 13, 1990
    Date of Patent: July 9, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: John E. Cunningham, Alastair M. Glass, Erdmann F. Schubert
  • Patent number: 5024967
    Abstract: A process is described for making semiconductor devices with highly controlled doping profiles. The process involves minimizing or eliminating segregation effects caused by surface electric fields created by Fermi-level pinning. These electric fields act on dopant ions and cause migration from the original deposition site of the doplant ions. Dopant ions are effectively shielded from the surface electric fields by illumination of the growth surfaces and by background doping. Also, certain crystallographic directions in certain semiconductors do not show Fermi-level pinning and lower growth temperatures retard or eliminate segregation effects. Devices are described which exhibit enhanced characteristics with highly accurate and other very narrow doping profiles.
    Type: Grant
    Filed: June 30, 1989
    Date of Patent: June 18, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Rose F. Kopf, J. M. Kuo, Henry S. Luftman, Erdmann F. Schubert
  • Patent number: 5018157
    Abstract: In a vertical cavity laser, such as an InP based vertical laser, the energy bandgap in the active region can be made equal to or larger than the bandgap in a semiconductor mirror stack by virtue of degenerate doping in the stack sufficient to suppress electronic band-to-band optical absorption. For example, the active region of an InP based laser can be lattice-matched GaInAs, GaInAsP, or a multiple quantum well structure composed of layers of InP and GaInAs--with the mirror stack composed of alternating layers of InP and degenerately doped n-type lattice-matched GaInAs or GaInAsP.
    Type: Grant
    Filed: January 30, 1990
    Date of Patent: May 21, 1991
    Assignee: AT&T Bell Laboratories
    Inventors: Dennis G. Deppe, Russell D. Dupuis, Erdmann F. Schubert
  • Patent number: 4980892
    Abstract: Optical systems which include a particular type of wavelength-tunable semiconductor laser are disclosed. Significantly, the active layer of the laser includes a doping superlattice layer. Even more significantly, wavelength-tunability is achieved by nonuniformly, optically and/or electrically pumping the laser.
    Type: Grant
    Filed: May 30, 1989
    Date of Patent: December 25, 1990
    Assignee: AT&T Bell Laboratories
    Inventors: John E. Cunningham, Timothy D. Harris, Erdmann F. Schubert, Jan P. van der Ziel
  • Patent number: 4974044
    Abstract: The use of alternating n and p type regions asymmetrically spaced in a semiconductor material yields extremely advantageous properties. In particular, by controlling the doping level and the spatial configuration of the doped region both the device response and its optical properties are controllable. Therefore, in applications such as those involving optical switches LEDs, lasers and long wavelength detectors, both the speed of device and its optical properties are controllable. As a result, greater fabrication flexibility than previously available is possible.
    Type: Grant
    Filed: April 21, 1989
    Date of Patent: November 27, 1990
    Assignee: AT&T Bell Laboratories
    Inventors: John E. Cunningham, Alastair M. Glass, Erdmann F. Schubert
  • Patent number: 4929064
    Abstract: Electromagnetic radiation is modulated in response to an electrical signal which produces a variable electric field in a semiconductor .delta.-doped structure. A resulting device has a desirably broad wavelength range in which light intensity can be modulated, large contrast ratio between transparent and opaque states, small operating voltage, and high-speed capability as desirable in optical communications applications.
    Type: Grant
    Filed: July 21, 1988
    Date of Patent: May 29, 1990
    Assignee: American Telephone and Telegraph Company
    Inventor: Erdmann F. Schubert
  • Patent number: 4784967
    Abstract: A method of fabricating a field-effect transistor is disclosed wherein only two masking steps are used in the development of the device. The semiconductor wafer used in the process has a non-alloyed contact at its top surface, that is, a contact which does not require alloying temperatures in excess of 200 degrees C. The first mask is used to create conventional mesa structures which isolate each individual field-effect transistor from its adjacent neighbors. A second mask is utilized to define the source and drain electrodes and also to create a gap through which the gate electrode structure is fabricated. By using a single mask for creation of both the source and drain electrodes and the gate structure, very close tolerances are obtained between the gate structure and the source and drain regions.
    Type: Grant
    Filed: December 19, 1986
    Date of Patent: November 15, 1988
    Assignee: American Telephone and Telegraph Company, AT&T Bell Laboratories
    Inventors: John E. Cunningham, Erdmann F. Schubert, Won-Tien Tsang