T.K. Woodward

1-Gb/s integrated optical detectors and receivers in commercial CMOS technologies

The ability to produce a high-performance monolithic CMOS photoreceiver, including the photodetector, could enable greater use of optics in short-distance communication systems. Such a receiver requires the ability to simultaneously produce a photodetector compatible with a high-volume high-yield CMOS process, as well as the entire receiver circuit. The quest for this element has yet to produce a clear winner, and has proven quite challenging. We review some of the work in this field with the goal of informing the reader as to the origin of the challenges and the implementation tradeoffs. Finally, we report experimental results from a monolithic CMOS photoreceiver realized in a 0.35-/spl mu/m production CMOS process, including a CMOS photodiode. Operating at 1 Gb/s, the receiver requires an average input power of -6.3 dBm at 850 nm to obtain a measured bit error rate of 1/spl times/10/sup -9/, and dissipates 1.5 mW at 2.2 V, increasing to 6 mW at 3.3 V.

Batch fabrication and operation of GaAs-Al/sub x/Ga/sub 1-x/As field-effect transistor-self-electrooptic effect device (FET-SEED) smart pixel arrays

The structure, processing, and performance of arrays of integrated field-effect transistor-self-electrooptic effects devices (FET-SEEDs) consisting of doped-channel field-effect transistors, multiple quantum-well (MQW) modulators, and p-i-n MQW detectors are discussed. The performance of the FETs and SEEDs such as g/sub m/ and contrast, is equivalent to that obtained when they are made separately. Typical values are g/sub m/=80 mS/mm and contrast of 3. The largest arrays contain 128 circuits. The circuits operate at speeds as fast as 500 Mb/s, with optical input switching energy of approximately=400 fJ. At 170 Mb/s, the required optical input switching energy is approximately=70 fJ. This optical energy is at least a factor of 20 less than for symmetric SEEDs (S-SEEDs) with the same optical window sizes. Hence, FET-SEEDs provide superior performance compared to conventional S-SEEDs. >

Optical receivers for optoelectronic VLSI

We describe our work on the design and testing of optical receivers for use in optoelectronic VLSI. The local nature of the optoelectronic VLSI system permits novel receiver designs, incorporating multiple optical beams and/or synchronous operation, while the requirement of realizing large numbers of receivers on a single chip severely constrains area and power consumption. We describe four different receiver designs, and their different operating modes. Results include 1-Gb/s high-impedance, two-beam diode-clamped FET-SEED receivers, single and dual-beam transimpedance receivers realized with a hybrid attachment of multiple-quantum well devices to 0.8-/spl mu/m linewidth CMOS operating to 1 Gb/s, and synchronous sense-amplifier-based optical receivers with low (/spl sim/1 mW) power consumption. Finally, we introduce a measure of receiver performance that includes area and power consumption.

InxGa1−xAs/GaAs multiple quantum well optical modulators for the 1.02–1.07 μm wavelength range

We report the operation of strained‐layer InxGa1−x As/GaAs 50‐ and 100‐period multiple quantum well optical modulators at wavelengths ranging from 1.02 to 1.07 μm. Structures were grown on GaAs substrates, as well as on strain relief InxGa1−xAs buffer layers. Devices show favorable electrical characteristics and absorption contrasts up to 57% at the exciton peak. Optical modulation of a Nd:YAG laser is demonstrated, via operation of self‐electro‐optic effect devices at 1.064 μm.

1-Gb/s two-beam transimpedance smart-pixel optical receivers made from hybrid GaAs MQW modulators bonded to 0.8 μm silicon CMOS

We have made two-beam smart-pixel optical receivers using a hybrid attachment of GaAs-AlGaAs multiple quantum-well (MQW) pin devices to foundry-fabricated 0.8-/spl mu/m linewidth CMOS circuits. Results from a repeater in which receiver output is coupled to a transmitter circuit driving a differential pair of MQW modulators are reported. When tested with high-contrast, directly-modulated laser diodes, an optical energy of 26 fJ (-21.5 dBm) in each beam is required to obtain a bit error rate of 1/spl times/10/sup -9/ at 622 Mb/s, and operation at this error rate is observed to 1 Gb/s. The described receiver (one of several we have made) has three amplification stages, with the first being of the transimpedance type. The reported receiver fits easily within a 45/spl times/25 /spl mu/m area, and the entire repeater circuit draws about 2 mA from a 5-V power supply, with the transmitter accounting for about 20 percent of the total.

Operation of a fully integrated GaAs-Al/sub x/Ga/sub 1-x/As FET-SEED: a basic optically addressed integrated circuit

The authors experimentally demonstrate the operation of a fully integrated optoelectronic circuit with optical input and output consisting of a p-i-n photodetector and load resistor, a depletion-mode GaAs-Al/sub x/Ga/sub 1-x/As heterostructure field-effect transistor (HFET) and self-biased HFET load, together with an output GaAs-Al/sub x/Ga/sub 1-x/As multiple quantum-well optical modulator. All elements have been monolithically integrated within a 50- mu m*50- mu m area. A low optical power input causes a modulation of a higher-power output, demonstrating optical signal amplification.<<ETX>>

InAsyP1−y/InP multiple quantum well optical modulators for solid‐state lasers

We report the operation of strained‐layer InAsyP1−y/InP multiple quantum well optical modulators at wavelengths compatible with solid‐state lasers such as neodymium‐doped yttrium aluminum garnet. A structure having 50 periods of 100 A InAsyP1−y quantum wells with 100 A InP barriers is described that has an exciton peak at 1.05 μm and a single pass transmission contrast ratio of 1.4. Favorable comparison is made to similar InxGa1−xAs/GaAs structures.

Experimental sensitivity studies of diode-clamped FET-SEED smart-pixel optical receivers

Experimental studies of monolithically integrated double-clamped smart-pixel optical receivers are presented. Circuits are realized in FET-SEED (field-effect transistor self-electrooptic effect device) integration technology, which permits fabrication of GaAs-based FETs, together with normal-incidence multiple-quantum-well detector/modulator devices. Novel features of the circuit include the use of two input signal beams, and the ability to control the input voltage swing with clamping diodes. Two variations of our circuit are found to have input capacitances of 50 or 60 fF. Resultant input optical switching energies depend on the voltage swing, the FET performance, and the input data format, but operation at 200 Mb/s with 40 fJ is demonstrated under ideal conditions with nonreturn-to-zero (NRZ) data. Finally, operation of the receiver with pulses that are short compared to the bit period is found to be advantageous as compared to the case of pulses equal to the bit period in length (NRZ format). 650 Mb/s operation is demonstrated. >

Multiple quantum well light modulators for the 1.06 μm range on InP substrates: InxGa1−xAsyP1−y/InP, InAsyP1−y/InP, and coherently strained InAsyP1−y/InxGa1−xP

We compare InP‐based materials systems for multiple quantum well modulator application in the 1.06 μm wavelength range. Quantum well/barrier systems studied are the lattice‐matched system InxGa1−xAsyP1−y/InP, the strained system InAsyP1−y/InP, and the strain‐balanced system InAsyP1−y/InxGa1−xP. 50 period samples were grown on InP substrates by chemical beam epitaxy. We find the ternary systems to be better than the quaternary in terms of exciton peak sharpness. The InAsyP1−y/InxGa1−xP system was best overall, with our results suggesting that it is coherently strained to the InP substrate.

Growth of strain-balanced InAsP/InGaP superlattices for 1.06 μm optical modulators

Using a strain‐balanced growth approach, we show that the pseudomorphic InAsP/InGaP multiple quantum well structures, grown by chemical beam epitaxy, have superior material properties for 1.06 μm modulator application when compared to the strained InAsP/InP or the lattice‐matched InGaAsP/InP systems. The broadening in absorption edge due to dislocations in the strained system, or composition fluctuations in the lattice‐matched system as a consequence of growth temperature instability, can be greatly minimized. A strong reduction in the nonradiative recombination centers in the strain‐balanced InAsP/InGaP system has been observed.