International Business Machines Corporation

Dennis L Rogers

John J Ellis-Monaghan

James William Adkisson

Mark David Jaffe

Mark B Ritter

Dale J Pearson

Min Yang

Mitchell S Cohen

Devendra K Sadana

Guy M Cohen

Kern Rim

Marie Angelopoulos

Jerry M Woodall

Daniel Michael Kuchta

Sandip Tiwari

Jeremy Daniel Schaub

Dan Moy

Young Hoon Kwark

Glen Walden Johnson

Ismail C Noyan

Albert X Widmer

Modest M Oprysko

Jeffrey John Welser

Sudhir Muniswamy Gowda

Mark F Bregman

Mark S Milshtein

George D Pettit

John D Crow

Andrew T Pomerene

Ravi S Ananth

Steve Koester

William D Brewer

David T McInturff

Jeanine M Trewhella

A method for manufacturing a pixel sensor cell that includes a photosensitive element having a non-laterally disposed charge collection region. The method includes forming a trench recess in a substrate of a first conductivity type material, and filling the trench recess with a material having second conductivity type material. The second conductivity type material is then diffused out of the filled trench material to the substrate region surrounding the trench to form the non-laterally disposed charge collection region. The filled trench material is removed to provide a trench recess, and the trench recess is filled with a material having a first conductivity type material. A surface implant layer is formed at either side of the trench having a first conductivity type material. A collection region of a trench-type photosensitive element is formed of the outdiffused second conductivity type material and is isolated from the substrate surface.

CMOS imager photodiode with enhanced capacitance

A pixel sensor cell having a semiconductor substrate having a surface; a photosensitive element formed in a substrate having a non-laterally disposed charge collection region entirely isolated from a physical boundary including the substrate surface. The photosensitive element comprises a trench having sidewalls formed in the substrate of a first conductivity type material; a first doped layer of a second conductivity type material formed adjacent to at least one of the sidewalls; and a second doped layer of the first conductivity type material formed between the first doped layer and the at least one trench sidewall and formed at a surface of the substrate, the second doped layer isolating the first doped layer from the at least one trench sidewall and the substrate surface. In a further embodiment, an additional photosensitive element is provided that includes a laterally disposed charge collection region that contacts the non-laterally disposed charge collection region of the photosensitive element and underlies the doped layer formed at the substrate surface.

A method of forming an avalanche trench optical detector device on a semiconductor substrate, comprising forming a first set and a second set of trenches in the substrate, wherein trenches of the first set are alternately disposed with respect to trenches of the second set, filling the trenches with a doped sacrificial material, and annealing the device to form a multiplication region in the substrate. The method comprises etching the doped sacrificial material from the first set of trenches, filling the first set of trenches with a doped material of a first conductivity, etching the doped sacrificial material from a second set of trenches, and filling the second set of trenches with a doped material of a second conductivity. The method further comprises providing separate wiring connections to the first set of trenches and the second set of trenches.

Method for fabricating avalanche trench photodetectors

A photodetector (and method for producing the same) includes a semiconductor substrate, a buried insulator formed on the substrate, a buried mirror formed on the buried insulator, a semiconductor-on-insulator (SOI) layer formed on the conductor, alternating n-type and p-type doped fingers formed in the semiconductor-on-insulator layer, and a backside contact to one of the p-type doped fingers and the n-type doped fingers.

Semiconductor-on-insulator lateral p-i-n photodetector with a reflecting mirror and backside contact and method for forming the same

A semiconductor device (and method for forming the device) includes a silicon-on-insulator (SOI) wafer formed on a substrate surface. An isolation trench in the wafer surface surrounds alternating p-type trenches and n-type trenches and electrically isolates the device from the substrate, thereby allowing the device to be effectively utilized as a differential detector in an optoelectronic circuit.

Silicon-on-insulator (SOI) trench photodiode

A monolithic semiconductor optical detector is formed on a substrate having a plurality of substantially parallel trenches etched therein. The trenches are further formed as a plurality of alternating N-type and P-type trench regions separated by pillar regions of the substrate which operate as an I region between the N and P trench regions. First and second contacts are formed on the surface of the substrate and interconnect the N-type trench regions and the P-type trench regions, respectively. Preferably, the trenches are etched with a depth comparable to an optical extinction length of optical radiation to which the detector is responsive.

Lateral trench optical detectors

A low noise, high gain-bandwidth preamplifier is formed which employs positive, capacitive feedback to compensate the frequency response of the amplifier for an applied input capacitance. The circuit includes a differential amplifier circuit with conventional resistive, negative feedback. The circuit further includes a pair of compensating capacitors coupled across the amplifier, providing positive feedback which compensates for an applied input capacitance. The preamplifier circuit provides a high gain-bandwidth along with enhanced noise performance.

Low noise, bandwidth compensated transimpedance amplifier

An automatic and adaptive threshold setting circuit for an IR receiver is capable of operating over a broad range of frequencies and power levels. The adaptive threshold circuit allows a very sensitive threshold in environments where little sunlight or other ambient light reaches the receiver, but which will increase the threshold of the receiver when large amounts of ambient light fall on the photo diode. The circuit senses the current flowing through the reverse biased IR photo detector due to ambient light levels. This current measurement is used to adjust the sensitivity of the receiver.

Automatic threshold setting circuit

A circuit that can switch between a peak detect and an averaging mode is described. In a preferred embodiment, when the circuit is in a peak detect mode a first transistor is on and a second is off, enabling an amplifier in the circuit to produce a signal representative of the peak value of an input signal. In an averaging mode, the first transistor is off, and a second transistor turns on, disabling the output of the amplifier, and thus enabling the averaging mode components of the invention.

Switchable peak/average detect circuit

Methods, apparatus and manufacturing processes are set forth which reduce the affects of scattered light in electro-optical devices, fiber optic links, etc., through the use of radiation sensitive compounds which, for example, can be easily applied to a semiconductor wafer when fabricating a solid state integrated receiver. According to the invention, a given radiation sensitive compound is transformed into a light blocking material (i.e., a material that will not transmit light) as a result of a lithographic (and in some cases a photolithographic) process. The resultant blocking material may be easily removed from any regions which is designed to receive transmitted light (for example, detector regions); while any other light sensitive regions remain covered (i.e., are protected) by the blocking material at the conclusion of the process.

Scattered light blocking layer for optoelectronic receivers

A direct optical connector (DOC) comprised of first and second members, each including a plurality of light emitting and light detecting locations, operative in combination with energy transfer media to form direct optical connections between the light emitting locations and the light detecting locations, wherein said first and second members are adapted for reclosable connection to each other whereupon the light emitting locations on one member are aligned with the light detecting locations on the other member. The first and second members of the preferred DOC are modular. Alternative forms of energy transfer media are used in various embodiments of the invention including lenslet arrays, imaging fiber plates (IFPs), and energy transfer fiber plates (ETFPs). These media have differing alignment criteria, differing degrees of immunity from crosstalk, differing degrees of transfer efficiency, different manufacturing costs, etc., thereby permitting the fabrication and/or use of a connector most suited to meet the requirements of a particular application. A modular half of a DOC can be used in conjunction with a remote optical connector (ROC) to channel light over relatively long distances. The invention also encompasses processes for fabricating ROCs.

Electro-optical connectors

A semiconductor photodetector is formed of interdigitated, metal-semiconductor-metal electrodes disposed on a surface of semi-insulating semiconductor material, gallium arsenide. Radiation such as infra-red or visible light is converted to an electric current flowing between the electrodes upon application of a bias voltage between the electrodes. A Schottky barrier at the junction of each electrode surface and the semiconductor surface limits current flow to that produced by photons. Tunneling of charge carriers of the current under the Schottky barrier, which tunneling results from the entrapment of charge carriers on the semiconductor surface, is inhibited by the production of a heterojunction surface layer upon the foregoing surface between the electrodes to repulse the charge carriers and prevent their entrapment at the surface. The heterojunction layer may be doped to enhance the repulsion of charge carriers. The heterojunction surface layer is of sufficient thickness to prevent tunneling of photogenerated carriers to a noncontacted region of the surface of the heterojunction layer and to also permit efficient repulsion of charge carriers from the surface. Longer wavelength photodetectors may also be formed in this way by providing misfit dislocation regions between the interaction region, which may be GaInAs, and a GaAs substrate, thereby providing a pseudo-morphic interaction region which is graded back to a heterojunction layer at the surface.

Heterojunction interdigitated schottky barrier photodetector

A semiconductor photodetector is formed of interdigitated, metal-semiconductor-metal electrodes disposed on a surface of semi-insulating semiconductor material, gallium arsenide. Radiation such as infra-red or visible light is converted to an electric current flowing between the electrodes upon application of a bias voltage between the electrodes. A Schottky barrier at the junction of each electrode surface and the semiconductor surface limits current flow to that produced by photons of sufficient frequency, or energy, to overcome the Schottky barrier. Tunneling of charge carriers of the current under the Schottky barrier, which tunneling results from the entrapment of charge carriers on the semiconductor surface, is inhibited by the production of a doped surface layer upon the foregoing surface between the electrodes to repulse the charge carriers and prevent their entrapment at the surface. The doped surface layer is much thinner than an interaction region of the radiation in the semiconductor material and has sufficiently high resistance to permit the photodetector to function efficiently.

Interdigitated Schottky barrier photodetector

A multi-stage current mode differential amplifier is disclosed in which each cascaded stage includes a pair of input transistors which have their bases connected to a common voltage source and a pair of control transistors which have their emitters connected to a common current source. A diode-like device is inserted between the collector of a control transistor in one stage and the emitter of an input transistor of the succeeding stage which increases the input impedance seen by the control transistor, thereby permitting an increase in amplification for that stage. In both embodiments, the current signal is amplified at a higher rate than the rate of increase of the bias currents supplied to the emitters of the control transistors in each stage. In one embodiment, the arrangement of the diode in the collector circuit of the control transistor permits the voltage sources connected to the bases of the input transistors to remain substantially constant for each cascaded stage in contrast to prior art devices where the voltages had to be increased for each additional stage.

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Carmel, NY, United States of America

Dennis L Rogers