We present a novel coupling scheme consisting of an integrated beam expander, a specifically tailored TiO/sub 2/ antireflection coating, optical index matching gel, and uncoated flat-end single-mode fiber (SMF). This scheme was used to package four-channel semiconductor optical amplifier arrays. Far-field profiles for each discrete amplifier in the array are typically 80 and 150 FWHM, perpendicular and parallel to the junction plane, respectively. The TiO/sub 2/ AR coating overcomes the indices mismatching of fiber glass and InP based device, and reduce optical reflection to 0.002% at 1.55 /spl mu/m. Misalignment tolerance in the l-dB excess loss range, for a discrete channel, is typically 5 /spl mu/m vertically and 8 /spl mu/m laterally. The average coupling loss is 4.3 dB per facet for the devices measured. Fiber coupled small signal gain for the amplifiers is typically 11.6 dB and a saturation output power of 3.0 dBm. The method of characterization and optimization of the TiO/sub 2/ coating is discussed.

We describe a single-port, reflective, waveguide modulator based on semiconductor laser amplifier technology, The single-port geometry reduces the high packaging cost associated with two-port waveguide modulators, while the internal gain of the amplifier compensates for splitting and coupling losses. A modulator with a bulk active layer showed a reflection-mode chip gain of 17 dB at lambda = 1.56 mu m. When driven with pseudorandom digital data at 100 Mb/s, extinction ratios of > 12 dB were observed over the broad wavelength range (20 nm) needed for wavelength division multiplexed systems. Bit-error-rate tests confirmed that there was no distortion penalty, compared to a LiNbO3 reference modulator.

Summary form only given. The present work studies the performance of a star-geometry self amplified network (SANE) with remote pumping. Moving the amplifier upstream and pumping it remotely increases the signal level at the amplifier input, improved the sensitivity while eliminating the need for a narrow bandpass optical filter to suppress amplified spontaneous emission (ASE).

Optoelectronic S-parameter measurements offer the bandwidth needed to characterize today's state-of-the-art transistors, but have not yet achieved the throughput or accuracy provided by a vector network analyzer with microwave probes. In this paper, we discuss a new approach in which movable optoelectronic probes, calibrated by testing simple standard devices, are stepped around the wafer to provide accurate, high-throughput S-parameter measurements. Sub-picosecond laser pulses drive photoconductive switches on the probe tips, to generate electrical stimulus pulses and define sampling intervals, and signals are transferred to and from the wafer under test by coplanar waveguide transmission lines and plated contact bumps. The probes provide electrical pulses as short as 3 psec (FWHM), while maintaining a broadband 50 ohm termination to ensure stability of the device under test. Since probe flexure under contact significantly disturbs alignment of free-space beams, fiber-optic input is used to improve reproducibility. Analysis by vector error correction in the frequency domain removes systematic errors and separates the incident and reflected pulses without subjective time-window gating. We have demonstrated precise measurement of the complex reflection coefficient S 11 at frequencies up to 175 GHz. Noise simulations have been performed to investigate the effect of various system parameters on the measurement uncertainty and useful bandwidth for S-parameter tests

We have constructed optoelectronic wafer probes with fiber pigtails and demonstrated accurate, reproducible measurements of the complex reflection coefficient Sll at frequencies up to 125 GHz. Vector accuracy enhancement routines, based on the measurement of known standard devices, are used to remove the effects of tip reflections and other systematic errors. Groundbridging straps are shown to suppress the mode conversion errors which result from asymmetric excitation of the coplanar waveguide probe.

Secondary ion mass spectrometry was used to study the effect of substrate temperature on the composition and growth rate of InGaAs/InP multilayers grown by chemical beam epitaxy. The dependence on the As overpressure was also studied for the first time by this technique. The substrate temperature effects that we observed are in good agreement with published results from x-ray diffraction and Auger electron spectroscopy studies. The Ga/In ratio was observed to decrease with increasing arsine flow rate in contradiction to previously reported results.

We have fabricated optoelectronic wafer probes with both free-space and fiber-optic input, and adapted microwave error correction techniques to enable calibrated measurements with the new probes. Photoconductive switches on the probe tip define stimulus pulses and sampling intervals, and signals are transferred to and from the wafer under test by coplanar waveguide transmission lines and plated contact bumps. Vector error correction eliminates the need for time gating to separate the input and reflected pulses, while enhancing accuracy. Since probe flexure under contact significantly disturbs alignment of free-space beams, fiber-optic input yields the most precise measurements. We demonstrate calibrated, on-wafer, measurements of the complex reflection coefficient S11 at frequencies up to 100 GHz.

We demonstrate the operation of a vacuum collector–semiconductor transistor based on negative electron affinity cold cathode technology. The unique aspect of this transistor is that the collector is separated from the emitter-base junction by a vacuum drift region, yielding an intrinsic collector capacitance which is an order of magnitude lower than that for conventional bipolar transistors. The collector charging time is thus proportionally smaller. Transport in the vacuum drift region is truly ballistic and depends only on the collector-base bias, enabling a wide range of device concepts which are impossible or impractical in conventional transistors.

Standard lithographic techniques have been utilized to fabricate quantum wells which are confined on both sides by vacuum. These "naked" quantum wells are fabricated from spatially and compositionally modulated III-V superlattices in which alternate layers of the structures are sacrificed by selective etching. These structures are patterned such that the quantum wells are suspended between support posts.

We have developed a process technology for direct-coupled FET logic (DCFL) circuits on InP substrates, based on enhancement-mode InGaAs/InAlAs heterostructure-insulated-gate FET's (HIGFET's), and demonstrated its performance by fabricating 11- and 19-stage ring oscillators. The circuits were fabricated on undoped lattice-matched heterostructures grown by MBE, using a refractory-gate process with self-aligned sidewalls to achieve a lightly-doped-drain (LDD) structure. For a gate length of 1.2-mu-m, with V(dd) = 2 V, the best propagation delay observed was 23 ps/stage, with associated power of 2.2 mW/stage.

Ultra thin (100-200 Å) AlGaAs emitter layers have been incorporated in AlGaAs/GaAs Heterojunction Bipolar Transistors (HBTs). Fabricated using a self-aligned process technology, this novel structure has yielded transistors with submicron emitter widths. The AlGaAs emitter layer serves to passivate the base surface resulting in constant current gain values of 25 for all geometries independent of emitter area. The maximum cutoff frequency obtained was 35 GHz with a corresponding 38 GHz for the maximum frequency of oscillation for a 1.3?m x 9 ?m emitter area device.

The authors report p-channel heterostructure FETs fabricated on InP substrates, as well as advanced results on submicrometer n-channel HIGFETs. P-HIGFETs with 1- mu m nominal gate lengths were made using lattice-matched InGaAs channels and InAlAs barriers. Threshold voltage and threshold uniformity were studied as a function of gate length for n-channel InGaAs/InAlAs HIGFETs in the range from 0.4 ...

The authors propose and demonstrate the integration of a photodiode, a quantum-confined Stark-effect quantum-well optical modulator, and a metal-semiconductor field-effect transistor (MESFET) to make a field-effect transistor self-electrooptic effect device. This integration allows optical inputs and outputs on the surface of a GaAs-integrated circuit chip, compatible with standard MESFET processi...

High aspect ratio submicron W gate structures as short as 0.1 μm have been made by e-beam lithography and reactive ion etching. An SF6/CHF3 gas mixture has been studied to limit the undercutting observed in SF6 alone. Etch profiles in 1-μm-high tungsten have been systematically studied as a function of gas composition and an optimum ratio found. Data will also be presented on etch selectivity, bias voltage effects, and overetching. High-performance InAlAs/InGaAs heterojunction-insulated-gate FETs (HIGFETs) incorporating W air-bridge gates as short as 0.3 μm have been made using this technology. These devices exhibit a unity current gain frequency ft of 80 GHz, as measured, and an estimated 118 GHz when corrected for pad capacitance. Both pinchoff characteristics and threshold voltage data have been measured for devices with gate lengths from 0.4 to 1.2 μm and are found to be suitable for enhancement mode operation.

A new, self-aligned process technology for AlGaAs/GaAs heterojunction bipolar transistors (HBT) has been developed, which is based upon ultrathin (100-200 AA) AlGaAs emitter layers. The thin AlGaAs emitter is used as a selective etch stop layer for contacting the p/sup +/ base layer and acts as an integral surface passivation layer which eliminates recombination currents in the extrinsic base regi...

Presents threshold voltage data for Al/sub 0.48/In/sub 0.52/As/Ga/sub 0.47/In/sub 0.53/As/InP heterostructure insulated gate FETs (HIGFETs) with gate lengths from 1.2 mu m to 0.4 mu m. The refractory-gate, self-aligned fabrication process was applied to MBE-grown structures with 300 AA Ga/sub 0.47/In/sub 0.53/As channels and semi-insulating superlattice buffers to achieve sharp pinchoff with excel...

In/sub 0.52/Al/sub 0.48/As/In/sub 0.53/Ga/sub 0.47/As/InP heterostructure insulated-gate field-effect transistors (HIGFETs) with gate lengths from 1.1 and 0.3 mu m have been fabricated, and their electrical performance is characterized at DC and microwave frequencies. The refractory-gate self-aligned process, applied to devices with In/sub 0.53/Ga/sub 0.47/As channels, yields an unprecedented combination of very-high speed and excellent uniformity. HIGFETs with L/sub g/=0.6 mu m showed average peak transconductance g/sub m/ of 528 mS/mm and unity-current-gain cutoff frequency f/sub t/ of 50 GHz. The uniformity of g/sub m/ was better than 1%, and the voltage of the g/sub m/ peak was uniform to +or-30 mV. HIGFETs with L/sub g/=0.3 mu m showed f/sub 1/ up to 63 GHz, but suffered from serious short-channel effect, due to excessive thickness of the InGaAs channel layer. A self-aligned technique for gate resistance reduction is shown to substantially improve microwave power gain.< >