Lucent Technologies Inc.

At&t Bell Laboratories

At+t Corp.

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

John E Cunningham

Keith Wayne Goossen

William Y Jan

Erdmann F Schubert

James Albert Walker

Won-Tien Tsang

Wayne Harvey Knox

Leo M Chirovsky

Rajiv N Pathak

Alastair M Glass

Sanghee Park Hui

Betty Jyue Tseng

Michael D Williams

Joseph Earl Ford

Ted Kirk Woodward

Ashok V Krishnamoorthy

Timothy D Harris

Lucian Arthur D'Asaro

Colin Alan Warwick

Tien-Heng Chiu

Jan P Van Der Ziel

John A Rentschler

Sergio Tsuda

A technique is described for determining the performance of substrate-side emitting VCSELs formed on a wafer. The technique involves forming top-emitting VCSELs on the same wafer as bottom-emitting VCSELs and then testing the top-emitting VCSELs and using the results to determine the performance of the bottom-emitting VCSELs of the wafer.

Method of making wafer having top and bottom emitting vertical-cavity lasers

A vertical cavity surface emitting laser emitting at about 1.3 microns while being optically pumped by a vertical cavity surface emitting laser emitting at about 810 nanometers characterized in that the resonant cavities of the two lasers are coupled to increase the effectiveness of the pumping light to stimulate emission from the gain medium of the long-wavelength medium. The two lasers are formed in a multilayer stack of which all the layers are epitaxial except for the layers at the top of the stack that serve as a broad band output mirror and the upper bounding of the long wavelength laser.

Vertical cavity surface emitting laser (VCSEL)

A semiconductor device having a buried doped layer of semiconductor material and a non-alloyed contact to the buried doped layer. The non-alloyed contact is made ohmic by the presence of an underlying delta-doped monolayer. The semiconductor device is made by placing a stop-etch layer on top of a buried doped layer and forming at least one delta-doped monolayer in either the stop-etch layer or the buried doped layer. Layers of semiconductor material disposed above the stop-etch layer are removed with an etchant to define an active region of the semiconductor device. The stop-etch layer prevents the etchant from removing the delta-doped monolayer. A non-alloyed metal film is then deposited over the delta-doped monolayer to form an ohmic contact to the buried doped layer.

Method of making a semiconductor device having a non-alloyed ohmic contact to a buried doped layer

A saturable Bragg reflector for use in mode locking a laser comprises a stack alternately of layers of a high index of refraction and layers of a low index of refraction. The layers of high index all have optical thicknesses of about one quarter the operating wavelength of the laser. The layers of low index, except for the pair of uppermost layers, have optical thicknesses of a quarter the operating wavelength but that pair have a thickness of about one eighth of a wavelength. A quantum well is located near the center of the layer of high index between the pair of one eighth wavelength. Such a reflector is used as one end of a resonant cavity that houses a gain medium.

Saturable bragg reflectors for use in mode-locking lasers

Wafer having top and bottom emitting vertical-cavity lasers

The present invention is an improved modelocked laser comprising an optical gain medium and an optical cavity including a self-tuning saturable reflector incorporating one or more quantum wells. In the improved laser, the self-tuning saturable reflector comprises a first Bragg grating having a reflection spectrum broader than the spectrum of desired lasing and an additional Bragg reflector for light in the spectral region of lasing to provide self-starting and stable operation without mechanical tuning. The Bragg reflectors are preferably semiconductor quarter wave reflector stacks, and the saturable absorber is one or more quantum wells within the outer stack. The invention also encompasses the new saturable reflector used in such lasers.

Modelocking laser including self-tuning intensity-dependent reflector

A flip-chip bonded VCSEL CMOS circuit for preventing rearwardly emitted photons from the VCSEL from interfering with CMOS operation. The CMOS has bonding pads affixed thereto and spaced apart to define a region. The VCSEL is mounted to the bonding pads so that a lower mirror of the VCSEL is positioned between the bonding pads and in close proximity to an upper, major surface of the CMOS. A blocking layer is provided and is positioned within the region defined by the bonding pads to absorb or reflect rearwardly emitted photons from the VCSEL. In another embodiment, the blocking layer is removed and a photon detector is formed in the CMOS for collecting the rearwardly emitted photons for use in determining, inter alia, VCSEL laser power.

Flip-chip bonded VCSEL CMOS circuit with silicon monitor detector

A method for thermocompression bonding structures together including structures having different coefficients of thermal expansion, for example, thermocompression bonding optical diode arrays or other semiconductor structures to silicon substrates to form electronic or optoelectronic devices. The method includes aligning and contacting the structures to be interconnected, thermocompressing the structures via their contact pad elements at a bonding temperature, establishing an encapsulation temperature, applying an encapsulant material between the bonded structures, and curing the encapsulant material at the encapsulation temperature. Conventional bonding processes, which treat encapsulation as a separate step apart from bonding processes, melt the bonded assembly together and include at least one thermal cycle in which the bonded assembly is cooled to room temperature and then is re-heated to the encapsulation temperature before applying the encapsulant material. The inventive method eliminates this thermal cycle by including encapsulation as an integral step in the thermocompression bonding process and therefore reduces or eliminates the possibility of damage to bonds or their multi-layered contact elements between the time of bonding and the time of encapsulation. Resultingly, the inventive method advantageously improves the quality and reliability of the resulting bonds within the formed device compared to bonds formed in a conventional manner.

Method for thermocompression bonding structures

The specification describes a process for growing device quality III-V heteroepitaxial layers without the use of buffer layers, i.e. largely defect free layers with thicknesses greater than 50 Angstroms directly on the III-V substrate. These high quality heteroepitaxial layers are grown by low temperature MBE.

Heteroepitaxial growth of III-V materials

Optoelectronic devices such as photodetectors, modulators and lasers with improved optical properties are provided with an atomically smooth transition between the buried conductive layer and quantum-well-diode-containing intrinsic region of a p-i-n structure. The buried conductive layer is grown on an underlying substrate utilizing a surfactant-assisted growth technique. The dopant and dopant concentration are selected, as a function of the thickness of the conductive layer to be formed, so that a surface impurity concentration of from 0.1 to 1 monolayer of dopant atoms is provided. The presence of the impurities promotes atomic ordering at the interface between the conductive layer and the intrinsic region, and subsequently results in sharp barriers between the alternating layers comprising the quantum-well-diodes of the intrinsic layer.

Process of making an optoelectronic devices utilizing multiple quantum

The disclosed novel doping method makes it possible to tailor the effective activation energy of a dopant species in semiconductor material. The method involves formation of very thin layers of .delta.-doped second semiconductor material in first semiconductor material, with the second material chosen to have a bandgap energy that differs from that of the first material. Exemplarily, in a Be-doped GaAs/AlGaAs structure according to the invention the effective activation energy of the dopant was measured to be about 4 meV, and in conventionally Be-doped GaAs it was measured to be about 19 meV. The invention can be advantageously used to dope III-V and II-VI semiconductors. In some cases it may make possible effective doping of a semiconductor for which prior art techniques are not satisfactory.

Articles comprising doped semiconductor material

A device having an optical modulation region and a photodetection region formed on a single wafer, and methods for making the device, are disclosed. In one configuration, the device consists of an off-axis nonpolar substrate that has, on one side, a region suitable for modulating an optical signal. The other side of the substrate has a region suitable for photodetection. The region suitable for modulating an optical signal includes a movable layer suspended over the substrate. As the movable layer moves under an applied voltage, the reflectivity of the modulation region changes. The photodetection region consists of a plurality of III-V layers. In a second configuration, the device consists of a III-V substrate that has a region for photodetection disposed on one surface. A region for optical modulation is disposed on the photodetection region.

Wafer level integration of an optical modulator and III-V photodetector

A process for manufacturing precise alloy compositions in nonlinear alloy systems. The invention implements a new quadratic fitting function that relates alloy composition c.sub.A for a variable A to input fluxes f.sub.A and f.sub.B, as c.sub.A =f.sub.A.sup.2 /(f.sub.A.sup.2 +/.beta.f.sub.B.sup.2). .beta. is a parameter that is used to modify the incorporation of the Group V input variable B. This modification is necessary because of different surface populations of Group V dimer species. This new fitting function precisely predicts alloy compositions in nonlinear systems, such as the GaAs.sub.l-y P.sub.y system, where y is set equal to the composition c.sub.A.

Method for producing a precise alloy composition from input variables

Low optical loss and simplified fabrication are achieved by a nonlinear reflector which incorporates one or more semiconductor quantum wells within an n half-wavelengths strain relief layer (where n is an odd integer greater than zero) that is formed on a standard semiconductor quarter wave stack reflector. Growth of the half-wavelength layer is controlled so that dislocations are formed in sufficient concentration at the interface region to act effectively as non-radiative recombination sources. After saturation, these recombination sources remove carriers in the quantum well before the next round trip of the optical pulse arrives in the laser cavity. The nonlinear reflector is suitable for laser modelocking at the high wavelengths associated with many currently contemplated telecommunications applications and provides, at such wavelengths, an intensity dependent response that permits it to be used for saturable absorption directly in a main oscillating cavity of a laser. Saturation intensity of the nonlinear reflector and thereby related laser modelocking properties can be controlled by disposing the quantum well(s) at a particular position within the strain relief layer.

Saturable Bragg reflector structure and process for fabricating the same

An in-situ method is disclosed for highly accurate lattice matching using reflection high energy electron diffraction dynamics. The method includes the steps of providing a substrate of a first semiconductor material and initiating growth of a second semiconductor material thereon. The oscillation amplitude of intensity I of waveform cycles is monitored using reflection high energy electron diffraction. A maximum intensity I.sup.+ and a minimum intensity I.sup.- is determined over a predetermined number of waveform cycles. The intensity drop .DELTA.I from initial reflectivity to minimum reflectivity of the waveform cycles is determined and normalized figure of merit FM is calculated for the predetermined number of waveform cycles using the relationship: ##EQU1## The fluxes of the second semiconductor material are then adjusted to maximize FM and optimize matching. A multiple quantum well light modulator is also provided including a semiconductor substrate of InP, a multiple quantum well region, disposed above the InP substrate, composed of InGaAs and having a thickness of about 4 .mu.m. The modulator is characterized by a lattice mismatch of less than 2.times.10.sup.4.

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Lincroft, NJ, United States of America

John E Cunningham