Development of a GaAs monolithic surface acoustic wave integratedcircuit

An oscillator technology using surface acoustic wave (SAW) delay lines integrated with GaAs MESFET electronics has been developed for GaAs-based integrated microsensor applications. The oscillator consists of a two-port SAW delay line in a feedback loop with a four-stage GaAs MESFET amplifier. Oscillators with frequencies of 470, 350, and 200 MHz have been designed and fabricated. This oscillator technology is most suitable for sensor applications but can logically be extended to radio-frequency oscillator and filter applications by methods well known for other piezoelectric substrates     

Electrooptic Bragg-diffraction modulators in GaAs/AlGaAsheterostructure waveguides

Reports theoretical and experimental results on electrooptic Bragg-diffraction modulators in GaAs/GaAlAs heterostructure waveguides. The devices utilize the linear electrooptic effect in periodic structures to facilitate spatial modulation of the refractive index in the waveguide. A numerical method was established to solve the waveguide equation and quantify the induced changes in the effective index of the waveguide as a result of reverse bias. The numerical calculation has established the guidelines for an optimum design of the modulator that operates in the Bragg regime. The measured diffraction efficiency of the single-grating Bragg modulator was as high as 90 percent at a driving voltage of 15 V. A device consisting of four such basic diffraction gratings was also fabricated and used to demonstrate the function of scalar addition. The highest bandwidth of the devices that have been measured exceeds 1 GHz. The planar waveguide Bragg modulators offer advantages including lower optical propagation loss, greater fabrication tolerance, and spatial separation between the diffracted and the undiffracted light beams     

GaAs low-power integrated circuits for a high-speed digital signalprocessor

A high-speed 4-bit ALU, 4×4-bit multiplier, and 8×8-bit multiplier/accumulator have been implemented in low-power GaAs enhanced/depletion E/D direct-coupled FET logic (DCFL). Circuits are fabricated with a high-yield titanium tungsten nitride self-aligned gate MESFET process. The 4-bit ALU performs at up to 1.2 GHz with only 131-mW power dissipation. The multiplication time for the 4×4-bit array multiplier is 940 ps, which is the fastest multiplication time reported for any semiconductor technology. The 8×8-bit two's complement multiplier/accumulator uses 4278 FETs (1317 logic gates) and exhibits a multiplication time of 3.17 ns. the fastest yet reported for a multiplier of this type. Yield on the best wafer for the 4×4-bit and 8×8-bit circuits is 94 and 43%, respectively. A digital arithmetic subsystem has been demonstrated, consisting of the 8×8-bit multiplier/accumulator, two of the 4-bit ALUs, three logical multiplexers, and a logical demultiplexer. The subsystem performs arithmetic and logic functions required in signal processing at clock rates as high as 325 MHz     

GaAs ICs for high-speed signal processing

A complete family of small-scale integration (SSI) and middle-scale integration (MSI) analog and digital GaAs ICs for real-time signal processing is reported. These circuits have been used on several microstrip PC board applications with clock frequencies ranging from 500 MHz to 1 GHz. Detailed circuit performances and future trends are presented and discussed     

A high-speed GaAs MESFET optical controller

Optical interconnects are being considered for control signal distribution in phased array antennas. A packaged hybrid GaAs optical controller with a 1:16 demultiplexed output that is suitable for this application is described. The controller, which was fabricated using enhancement/depletion mode MESFET technology, operates at demultiplexer-limited input data rates up to 305 Mb/s and requires less than 200 μW optical input power     

Measurement of a very high-speed InGaAs photodiode using electro-optic sampling

We demonstrate an eleclro-optic sampling system for the characterisation of very high-speed, long-wavelength photodetectors. The system uses a mode-locked InGaAsP injection laser operating at 1.3 ?m as the source of pump and sampling pulses.     

Calibration of sampling oscilloscopes with high-speed photodiodes

We calibrate the magnitude and phase response of equivalent-time sampling oscilloscopes to 110 GHz. We use a photodiode that has been calibrated with our electrooptic sampling system as a reference input pulse source to the sampling oscilloscope. We account for the impedance of the oscilloscope and the reference photodiode and correct for electrical reflections and distortions due to impedance mismatch. We also correct for time-base imperfections such as drift, time-base distortion, and jitter. We have performed a rigorous uncertainty analysis, which includes a Monte Carlo simulation of time-domain error sources combined with error sources from the deconvolution of the photodiode pulse, from the mismatch correction, and from the jitter correction.     

Studies of high-speed metal-semiconductor-metal photodetector witha GaAs/AlGaAs/GaAs heterostructure

A GaAs/AlGaAs/GaAs heterostructure metal-semiconductor-metal photodetector (HMSM) with an active area of 100 μm×100 μm was developed and studied. The measured risetime of the device is 30 ps. The measured falltime is as short as 23 ps. The observed ultrafast response is attributed to the reduction of both the carrier transit time and the device capacitance due to the incorporation of the AlGaAs barrier layer. The HMSM is found to have a smaller saturation capacitance and saturates at a much lower bias voltage in comparison with the conventional MSM photodetector (CMSM). At a bias of 10 V, the full width at half maximum (FWHM) of the temporal response of the HMSM is more than 20% smaller than that of the CMSM. In addition, it is found that the peak impulse response for the HMSM is substantially larger than that of the CMSM under the same operation condition. Two-dimensional and equivalent circuit analyses were carried out to interpret the observed phenomena and to provide insight into the underlying physics     

GaAs switched-capacitor circuits for high-speed signal processing

Switched-capacitor building blocks are presented which are suitable for implementation in GaAs MESFET technology. They include gain stages, operational amplifiers, and transmission gates. Switched-capacitor design techniques are discussed that minimize filter sensitivity to GaAs op-amp limitations. Experimental results are presented on a variety of GaAs switched-capacitor circuits, including a gain stage, a second-order bandpass filter, and a third-order low-pass filter. The circuits demonstrate sampling rates exceeding 100 MHz without significant loss of accuracy.     

Electron-beam fabricated high-speed digital GaAs integrated circuits

The fabrication and performance of high-speed GaAs logic circuits incorporating submicrometer gate length FET's fabricated by electron-beam lithography are discussed. The process technology required for realizing 0.5-µm gate length devices is detailed. High-speed results including a 10-GHz logic gate, 34-ps gate delay for a ring oscillator, and a 4-GHz flip-flop are described.     

Large-area, high-speed PIN detectors in GaAs

A large-area, lateral PIN detector which exhibits an 8 GHz bandwidth is reported. This device topology is ideally suited for monolithic integration with IC components.     

Feedback FET logic: a robust, high-speed low-power GaAs logicfamily

Feedback FET logic (FFL) with a special output stage that enables it to drive high on-chip capacitances with low power is discussed. FFL is robust in the face of process and temperature variations. The basic FFL gate is a NOR, but complex gates such as AND-OR-NOT are also practical. FFL is two to four times faster than comparable GaAs direct-coupled FET logic and Si CMOS and Si BiCMOS when driving on-chip capacitances that are typical of large ICs. FFL power at 200 MHz is also lower than CMOS and BiCMOS power by a factor of 2 to 4     

Overview of complementary GaAs technology for high-speed VLSIcircuits

A self-aligned complementary GaAs (CGaAs) technology (developed at Motorola) for low-power, portable, digital and mixed-mode circuits is being extended to address high-speed VLSI circuit applications. The process supports full complementary, unipolar (pseudo-DCFL), source-coupled, and dynamic (domino) logic families. Though this technology is not yet mature, it is years ahead of CMOS in terms of fast gate delays at low power supply voltages. Complementary circuits operating at 0.9 V have demonstrated power-delay products of 0.01 μW/MHz/gate. Propagation delays of unipolar circuits are as low as 25 ps. Logic families can be mixed on a chip to trade power for delay. CGaAs is being evaluated for VLSI applications through the design of a PowerPC-architecture microprocessor     

Picosecond optical sampling of GaAs integrated circuits

Direct electrooptic sampling is a noncontact optical-probing technique for measuring with picosecond time resolution the voltage waveforms at internal nodes within GaAs integrated circuits. The factors contributing to system bandwidth, sensitivity, spatial resolution, and circuit perturbation are discussed, as are the circuit requirements for realistic testing of analog and digital devices. Measurements of high-speed GaAs integrated circuits are presented, including time-domain waveform and timing measurements of digital and analog circuits and frequency-domain transfer function measurements of microwave circuits and transmission structures     

Dual-channel bootstrapped switch for high-speed high-resolution sampling

A novel low-voltage CMOS bootstrapped switch has been designed. In this switch, a PMOS-type bootstrapped circuit combining with an NMOS-type one forms a dual-channel sampling switch that transmits the input signals to the output. Because of this parallel structure, the variation of on-resistance, owing to the variation of the gate overdrive and the threshold voltage, is greatly reduced, exhibiting gain in the sample-and-hold accuracy and linearity. The design was realised in an SMIC 0.18 mum CMOS process and its greatly improved dynamic performance was measured     

Electrooptic sampling evaluation of 1.5 μmmetal-semiconductor-metal photodiodes by soliton compressedsemiconductor laser pulses

An electrooptic sampling system using soliton compressed pulses from a gain switched laser diode was assembled and used to characterize an InGaAs metal-semiconductor-metal photodetector at the important optical fiber wavelength of 1.55 microns. The measured rise time of the photodiode pulse was 6.5 ps. The pump and probe pulses had a FWHM of 0.6 ps as measured by autocorrelation. The sampling system rise time was evaluated to be 2.0 ps, yielding the estimated intrinsic photodiode rise time of 2.3 ps. By introducing a differential detection scheme and optical filtering, a shot noise limited sensitivity of 0.6 mV/Sqrt[Hz] was achieved. These results represent the fastest rise time, and most sensitive semiconductor laser based, electrooptic sampling system reported to date     

Direct electro-optic sampling of transmission-line signals propagating on a GaAs substrate

We report a new picosecond electro-optic sampling probe suitable for noncontact electronic characterisation of high-speed monolithic GaAs integrated circuits.     

GaAs HBT's for high-speed digital integrated circuit applications

GaAs HBT technology has emerged as one of the most important developments for digital circuits operating at clock frequencies of 100 MHz and higher. High-speed frequency dividers operating as high as 34.8 GHz and VLSI circuits as complex as 32-b CPU's operating at 200-MHz clock rate have been demonstrated. This paper reviews the role of GaAs HBT technologies for high-speed digital IC applications. The requirements for high-speed IC's and the characteristics of various HBT device structures and logic families are discussed. A summary of published results of the ultrahigh-speed circuits and the status of several high-speed VLSI circuits are presented to provide a guide for future developments     

Monolithic GaAs photoreceiver for high-speed signal processing applications

High-speed planar monolithically integrated GaAs photoreceivers have been fabricated by selective ion implantation into SI GaAs substrates. Their fabrication is fully compatible with existing GaAs LSI process schedules. A receiver upper cutoff frequency of 1.5 GHz and sensitivity of 112 V/W have been measured. The application of these devices in short-haul high-bit-rate data communication systems has been demonstrated in a 560 Mbit prototype optical data link, using packaged and fibre-coupled devices.