At&t Bell Laboratories

Bell Telephone Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

Louis A Koszi

Bertram Schwartz

Robert Louis Hartman

Richard W Dixon

David Alan Ackerman

Avishay Katz

Richard C Miller

William C Dautremont-Smith

Bryan P Segner

Peter M Thomas

Marc Ilegems

William Baxter Joyce

Philip J Anthony

Cyril J Mogab

Norman E Schumaker

Walter R Holbrook

Leonard J Ketelsen

John L Zilko

Marlin W Focht

Wilfried R Wagner

Richard S Williams

Franklin R Nash

Lasers for use in multichannel analog optical fiber communication systems (e.g., of the type contemplated for CATV) have to meet very stringent requirements, including high linearity. DFB lasers are advantageously used in such communication systems. Typically only a relatively small percentage of the nominally identical DFB lasers on a wafer meet the specifications. It has now been discovered that the likelihood that a given DFB laser will meet the requirements is substantially increased if the laser comprises means that are adapted for producing a non-uniform photon density in the laser cavity, with the density of photons being larger in the rear portion of the cavity than in the front portion, such that during operation of the laser the gain in the back portion is substantially independent of the laser current, whereas the gain in the front portion is a function of the laser current. A particular embodiment of the invention is a 'bare patch' DFB laser having a grating that extends only part way from the front facet towards the back facet, such that a portion of the laser cavity does not have the grating associated therewith. The design ensures that the proper photon density is established within the laser cavity with high probability, largely independent of the rear (HR) facet reflection phase.

Analog optical fiber communication system, and laser adapted for use in

Disclosed is a method of making a semiconductor device that exemplarily comprises depositing a Ti/Pt layer onto a AuBe intermediate layer on a p-doped region of a semiconductor body. It also comprises depositing a Ti/Pt layer onto a n-doped region of the semiconductor body, or onto a AuGe intermediate layer on the n-doped region, followed by rapid thermal processing. Exemplarily, the device is a semiconductor laser, the n-doped region is InP, the p-doped region is InGaAs or InGaAsP, and RTP involves heating in the range 425.degree.-500.degree. C. for 10-100 seconds. The method comprises fewer processing steps than typical prior art methods, reduces the danger of fabrication error and of wafer breakage and, significantly, results in contacts that can be relatively thermally stable and can have very low specific contact resistance (exemplarily as low as 10.sup.-7 .OMEGA..multidot.cm.sup.2).

Method of making a semiconductor device

The inventive method of producing a device having non-alloyed ohmic contacts of common composition to both an n-doped and a p-doped region of a semiconductor body comprises deposition of a Ti/Pt layer on the p-doped as well as the n-doped region, followed by rapid thermal processing (RTP). Exemplarily, the device is a semiconductor laser, the n-doped region is InP, the p-doped region is InGaAs or InGaAsP, and RTP involves heating in the range 425.degree.-475.degree. C. for 10-100 seconds. The method comprises fewer processing steps than typical prior art methods, reduces the danger of fabrication error and of wafer breakage and, significantly, results in contacts that can be relatively thermally stable and can have very low specific contact resistance (exemplarily as low as 10.sup.-7 .OMEGA..multidot.cm.sup.2).

Rapid thermal processing method of making a semiconductor device

A method for aligning an opto-electronic device such as a semiconductor laser to a waveguide on a substrate is disclosed. The method comprises placing the device onto the substrate such that it is in rough alignment with the waveguide, optically pumping the device such that the device emits electromagnetic radiation, with some of the emitted radiation being coupled into the waveguide and detected by appropriate means. If indicated by the detector signal, the position of the device is then adjusted until the desired degree of coupling is attained, whereupon the device is mechanically secured to the substrate and appropriate electrical connections made between device and substrate. Devices useful in the practice of the method typically comprise a window in their top metallization layer.

Article comprising an opto-electronic device and an optical waveguide

A contact structure and method of bonding III-V semiconductors which prevents shorting of the edges of the semiconductor chip and also allows the chip to be bonded with either major surface facing upward. Both surfaces include a gold pad surrounded by a material which is immiscible with the preform metal used to bond the chip to an outside surface. During fluxless bonding between the gold pad on one surface of the chip and the preform, the preform metal is prevented from wetting the edges of the chip. The opposite surface of the chip can be electrically contacted by wire bonding to the gold pad on that surface.

Contacts to III-V semiconductors

The property of materials in the GaAs/AlGaAs system, whereby at certain doses proton bombarded n-type material becomes highly resistive but p-type material remains highly conductive, is utilized to fabrication of integrated circuits which include buried semiconductor interconnections or bus bars between devices.

Method of making integrated circuits employing proton-bombarded AlGaAs

The property of Group III-V compound materials, whereby ion bombarded material becomes highly resistive but recovers its original low resistivity by annealing at a temperature which is dopant and material dependant, is utilized to fabricate integrated circuits which include buried semiconductor interconnections or bus bars between devices.

Production of semiconductor structures with buried resistive or

A method of producing patternable resistive regions in III-V compound semiconductor devices and a resulting device structure having improved current characteristics. III-V semiconductor substrates are irradiated with inert ions to produce a resistive region therein. At least one epitaxial layer is grown over the substrate while maintaining the resistive characteristics within the substrate. A second resistive region is then formed in at least the top epitaxial layer. This second resistive region is aligned with the first one in order to minimize current spread through the device.

Method of improving current confinement in semiconductor lasers by inert

Semiconductor light emitting devices, lasers and LEDs, are described in which the current flow channel is narrower near the top surface of the device and wider at its bottom near the active region. Also, described are several attenuation masks for fabricating the channels of these devices by particle bombardment.

Method of forming current confinement channels in semiconductor devices

A TJS light emitting diode (laser or LED) comprises an isotype double heterostructure (DH) and a V-groove which penetrates the intermediate layer of the DH. The groove is filled with a region of semiconductor material which enables carrier injection to occur from the region into the intermediate layer, or conversely, depending on the relative bandgaps of the layer and region. Real-refractive index guiding by the groove is described.

Stripe-guide TJS laser

Current confinement in semiconductor light emitting devices

Semiconductor lasers and LEDs are described in which the pumping current is constrained to flow from a relatively narrow upper channel formed by a V-groove, which extends to a depth short of the active region, through a relatively wider lower channel bounded by high resistivity regions, which extend from at least that depth into or through the active region. Also described are devices in which the V-groove is refilled with semiconductor material.

V-Groove semiconductor light emitting devices

A double heterostructure light emitting semiconductor device is described wherein a narrow bandgap active region is sandwiched between two wider bandgap cladding layers, one of which contains a p-n homojunction. The purpose is to separate the p-n junction from the active region and, thus, to have the active region bounded by two isotype (p-p or n-n) heterojunctions. This configuration significantly reduces nonradiative interface recombination current which occurs principally at the anisotype (p-n) heterojunction in a standard double heterostructure.

Light emitting semiconductor devices

A buried double heterostructure laser device isdescribed. A wafer of double heterostructure material is formed into narrow mesa stripes. A native oxide coating is formed on the side walls of the mesa. Semiconductor material having an index of refraction which is closely matched to the index of the active region is deposited over the mesa structure. High resistivity polycrystalline material forms on the native oxide and monocrystalline material forms on the top of the mesa. Vertical carrier and optical confinement is achieved by the higher bandgap cladding layers of the double heterostructure configuration. The native oxide acts as an electrical insulator to confine pumping current to the mesa. The closely matched polycrystalline material confines light parallel to the junction plane and prevents excitation of higher order transverse modes. Devices have been fabricated which exhibit cw threshold currents at room temperature as low as 55 mA.

Buried double heterostructure laser device

Plasma etching is described as a selective etch for dielectric masks such as SiO.sub.2, Si.sub.3 N.sub.4 and certain photoresists in the presence of native oxides of Group III-V compound semiconductors. This process can be used in the fabrication of mesa junction lasers and Burrus light emitting diodes.

Growing community of inventors

Scotch Plains, NJ, United States of America

Louis A Koszi