High Gain-bandwidth Product Research Articles

Recent advances in Ge/Si PIN and APD photodetectors

AbstractPhotodetectors on a Si platform are important because of the opportunity to manufacture literally millions of photodetectors per wafer and because the use of a mature CMOS (Complementary Metal‐Oxide‐Semiconductor) process results in low cost and high uniformity. In this paper, we review recent results on Ge‐Si‐based PIN‐type photodetectors and avalanche photodetectors (APD). We show several exciting advantages of SiGe photodetectors namely, the higher thermal conductivity of Si and Ge, resulting in higher power capability, and the lower k factor, resulting in higher gain bandwidth products in APDs (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Noise Concerns and Remedies in VXI and PXI Systems

For optimum performance, a modern, high performance, synthetic instrument must be designed to keep RF energy that is outside the module from leaking in-and not let any of its energy leak out into other modules. Every detail must be addressed. DC power lines, signal lines, air cooling holes, and conventional RF shielding are all important design considerations in the small confines of an SI chassis. Faster digital logic and amplifiers with excessively high gain-bandwidth products increase the design challenge of fielding a clean, high performance synthetic instrument. Each block of an Si-based system connects to another element or subsystem. Removing the mechanisms for spurs to propagate from one module to another is as important as removing the original source of the spur.

Mask Programmable CMOS Transistor Arrays for Wideband RF Integrated Circuits

A mask programmable technology to implement RF and microwave integrated circuits using an array of standard 90-nm CMOS transistors is presented. Using this technology, three wideband amplifiers with more than 15-dB forward transmission gain operating in different frequency bands inside a 4-22-GHz range are implemented. The amplifiers achieve high gain-bandwidth products (79-96 GHz) despite their standard multistage designs. These amplifiers are based on an identical transistor array interconnected with application specific coplanar waveguide (CPW) transmission lines and on-chip capacitors and resistors. CPW lines are implemented using a one-metal-layer post-processing technology over a thick Parylene-N (15 mum ) dielectric layer that enables very low loss lines (~0.6 dB/mm at 20 GHz) and high-performance CMOS amplifiers. The proposed integration approach has the potential for implementing cost-efficient and high-performance RF and microwave circuits with a short turnaround time.

Traveling Wave Amplification within a Waveguide

A novel amplification mechanism of traveling TM wave on an electron beam within a waveguide structure is proposed. Under boundary constraint of the waveguide, a hybrid coupling of longitudinal plasma wave and transverse guided one occurs to result in traveling instability. The instability refers to a backward traveling amplification. The new amplification in the waveguide due to the interactive coupling between the space charge mode and the waveguide one is firstly pointed out. The analysis is extended to the relativistic energy range to get a large gain. The features and properties are discussed for a wide frequency range as well as a high gain-bandwidth product.

Separate Absorption-Charge Multiplication Heterojunction Phototransistors With the Bandwidth-Enhancement Effect and Ultrahigh Gain-Bandwidth Product Under Near Avalanche Operation

We demonstrate a high-performance heterojunction phototransistor (HPT): separate absorption-charge multiplication HPT. The incorporation of an In0.52Al0.48 As-based multiplication layer in the In0.53 Ga0.47As-based collector layer of our HPT allows for a great shortening of the trapping time ( ~ ns to ~ 30 ps) of electrons at the base-emitter junction under near avalanche operation, without sacrificing the gain performance. The interaction between the photoconductive gain and avalanche gain means that it is not necessary to use high bias voltages (> 30 V ) in our device to attain high-gain (> 1times 104) performance. With this device design, we can achieve an extremely high (90 THz) gain-bandwidth product (1.6 GHz, 5.5 times 104) under a 6-V bias.

Enhancing power analysis attacks against cryptographic devices

A current-measuring technique is introduced, which promises to substantially enhance power analysis attacks against cryptographic co-processors. The proposed technique exploits an active circuit to measure the instantaneous current consumption of a device under attack while supplying, at the same time, the device with a stable voltage. Higher gain-bandwidth product, higher sensitivity and lower insertion error are the main advantages with respect to a resistor-based measurement. Experimental results when the proposed circuit is used to measure the current consumption of an FPGA are reported, and the achievable advantage in terms of sensitivity is discussed. Results of a differential power analysis attack are reported too.

40 Gbit/s waveguide avalanche photodiode with p-type absorption layer and thin InAlAs multiplication layer

Waveguide avalanche photodiodes exhibiting both wide bandwidth and high gain bandwidth product have been developed. An absorption layer includes a p-type quasi-field-formed layer and a multiplication layer consists of InAlAs with a low ionisation rate ratio. Optimisation of the design yielded superior performance such as a wide bandwidth of 36.5 GHz, a gain band width of 170 GHz and a high quantum efficiency of 0.75 A/W.

Detrimental effect of impact ionization in the absorption region on the frequency response and excess noise performance of InGaAs-InAlAs SACM avalanche photodiodes

It is shown that optimization of the electric field profile in the absorption region of separate absorption, charge, and multiplication InGaAs-InAlAs avalanche photodiodes is critical to achieve low excess noise and high gain bandwidth product.

Broad-band MMICs based on modified loss-compensation method using 0.35-/spl mu/m SiGe BiCMOS technology

Using the concept of loss compensation, novel broad-band monolithic microwave integrated circuits (MMICs), including an amplifier and an analog multiplier/mixer, with LC ladder matching networks in a commercial 0.35-/spl mu/m SiGe BiCMOS technology are demonstrated for the first time. An HBT two-stage cascade single-stage distributed amplifier (2-CSSDA) using the modified loss-compensation technique is presented. It demonstrates a small-signal gain of better than 15 dB from dc to 28 GHz (gain-bandwidth product=157 GHz) with a low power consumption of 48 mW and a miniature chip size of 0.63 mm/sup 2/ including testing pads. The gain-bandwidth product of the modified loss-compensated CSSDA is improved approximately 68% compared with the conventional attenuation-compensation technique. The wide-band amplifier achieves a high gain-bandwidth product with the lowest power consumption and smallest chip size. The broad-band mixer designed using a Gilbert cell with the modified loss-compensation technique achieves a measured power conversion gain of 19 dB with a 3-dB bandwidth from 0.1 to 23 GHz, which is the highest gain-bandwidth product of operation among previously reported MMIC mixers. As an analog multiplier, the measured sensitivity is better than 3000 V/W from 0.1 to 25 GHz, and the measured low-frequency noise floor and corner frequency can be estimated to be 20 nV/sqrt(Hz) and 1.2 kHz, respectively. The mixer performance represents state-of-the-art result of the MMIC broad-band mixers using commercial silicon-based technologies.

A Highly Linear CMOS Baseband Chain for Wideband Wireless Applications

The emergence of wide channel bandwidth wireless standards requires the use of a highly linear, wideband integrated CMOS baseband chain with moderate power consumption. In this paper, we present the design of highly linear, wideband active RC filters and a digitally programmable variable gain amplifier. To achieve a high unity gain bandwidth product with moderate power consumption, the feed-forward compensation technique is applied for the design of wideband active RC filters. Measured results from a 0.5 µm CMOS prototype baseband chain show a cutoff frequency of 10 MHz, a variable gain range of 33 dB, an in-band IIP3 of 13 dBV, and an input referred noise of 114 µVrms while dissipating 20 mW from a 3 V supply.

Recent Advances in Avalanche Photodiodes

The development of high-performance optical receivers has been a primary driving force for research on III-V compound avalanche photodiodes (APDs). The evolution of fiber optic systems toward higher bit rates has pushed APD performance toward higher bandwidths, lower noise, and higher gain-bandwidth products. Utilizing thin multiplication regions has reduced the excess noise. Further noise reduction has been demonstrated by incorporating new materials and impact ionization engineering with beneficially designed heterostructures. High gain-bandwidth products have been achieved waveguide structures. Recently, imaging and sensing applications have spurred interest in low noise APDs in the infrared and the UV as well as large area APDs and arrays. This paper reviews some of the recent progress in APD technology.

A 1-17-GHz InGaP-GaAs HBT MMIC analog multiplier and mixer with broad-band input-matching networks

An InGaP-GaAs heterojunction bipolar transistor (HBT) analog multiplier/mixer monolithic microwave integrated circuit (MMIC) is developed that adopts a Gilbert-cell multiplier with broad-band input-matching networks to widen the bandwidth up to 17 GHz. This MMIC was fabricated using a commercially available 6-in InGaP-GaAs HBT MMIC process. It achieved a measured sensitivity of above 1100 V/W for an analog multiplier and a conversion gain of better than 9 dB for a mixer. It also demonstrated a lower corner frequency and noise than that of an InP HBT analog multiplier. The measured low-frequency noise was 10 nV/sqrt(Hz), which is about half of that of an InP HBT analog multiplier with a similar architecture. The corner frequency of the low-frequency noise was roughly estimated to be 15 kHz. The measured performance of this MMIC chip with gain-bandwidth-product (GBP) of 47 GHz rivals that of the reported GaAs-based analog multipliers and mixers. The high GBP result achieved by this chip is attributed to the HBT device performance and the broad-band input-matching network.

Noise Analysis of InP/InGaAs Superlattice Avalanche Photodiode

A theoretical study of the noise characteristics of an InP/In0.53 Ga0.47 As Superlattice Avalanche photodiode (SL-APD) has been presented. It has been found that an improvement in the value of the effective hole-to-electron ionisation rate ratio (βeff/αeff) for the SL-APD structure results in a low-noise behaviour of the device. The device has a very high gain-bandwidth product (≈450 GHz) and a low excess noise factor at moderate gain. It is expected to find application as a highly sensitive low-noise photodetector in optical receiver unit for long-haul fiber optic communication system in 1.3 to 1.6 μm.

High Speed Resonant-Cavity InGaAs/InAlAs Avalanche Photodiodes

The evolution of long-haul optical fiber telecommunications systems to bit rates greater than 10 GB/s has created a need for avalanche photodiodes (APDs) with higher bandwidths and higher gain-bandwidth products than are currently available. It is also desirable to maintain good quantum efficiency and low excess noise. At present, the best performance (f3dB ~ 15 GHz at low gain and gain-bandwidth product ~ 150 GHz) has been achieved by AlInAs/InGaAs(P) multiple quantum well (MQW) APDs. In this paper we report a resonant-cavity InAlAs/InGaAs APD that operates near 1.55 μm. These APDs have achieved very low noise (k equivalent to 0.18) as a result of the very thin multiplication regions that were utilized. The low noise is explained in terms of a new model that accounts for the non-local nature of impact ionization. A unity-gain bandwith of 24 GHz and a gain-bandwidth-product of 290 GHz were achieved.

HIGH SPEED RESONANT-CAVITY InGaAs/InAlAs AVALANCHE PHOTODIODES

The evolution of long-haul optical fiber telecommunications systems to bit rates greater than 10 GB/s has created a need for avalanche photodiodes (APDs) with higher bandwidths and higher gain-bandwidth products than are currently available. It is also desirable to maintain good quantum efficiency and low excess noise. At present, the best performance (f3dB ~ 15 GHz at low gain and gain-bandwidth product ~ 150 GHz) has been achieved by AlInAs/InGaAs(P) multiple quantum well (MQW) APDs. In this paper we report a resonant-cavity InAlAs/InGaAs APD that operates near 1.55 μm. These APDs have achieved very low noise (k equivalent to 0.18) as a result of the very thin multiplication regions that were utilized. The low noise is explained in terms of a new model that accounts for the non-local nature of impact ionization. A unity-gain bandwith of 24 GHz and a gain-bandwidth-product of 290 GHz were achieved.

A high-efficiency distributed amplifier by using varying impedance

This paper develops a new kind of distributed amplifier with a higher gain–bandwidth product and more efficiency than a common distributed amplifier by using varying impedance. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 339–341, 2000.

An 8 channel GaAs IC front-end discriminator for RPC detectors

Abstract Although not traditionally considered for particle detector readout, circuit solutions based upon GaAs IC technologies can offer considerable performance advantages in high speed detector signal processing: high f T devices, such as the GaAs MESFET, allow the realization of front-end tuned amplifiers and comparators with the same detector time resolution. Such a feature is well-suited for RPC particle detectors, characterized by short pulse duration and constant shaping responses. A new design procedure shows the suitability of high speed narrow band GaAs amplifiers as voltage-sensitive input stages of front-end discriminators to perform the required voltage amplification for the following comparator, ensuring, at the same time, SNR optimisation, high gain and low power consumption. As an application of the proposed approach, a full-custom analog chip has been designed and realized using 0.6 μm GaAs MESFET technology from Triquint foundry. Eight channels of a front-end discriminator composed of a tuned voltage preamplifier followed by a high speed comparator have been realized with a resulting die size of 1.5×2.3 mm 2 . The chip turns out to be very stable, featuring high voltage gain (>1000), high gain-bandwidth product (10 11 ) and low sensitivity (∼50 μV), fast rise time (1.5 ns) and a power consumption of 25 mW per channel. It has been successfully tested as front-end stage in RPC trigger detectors.

High Performance CMOS Transconductor for Mixed-Signal Analog-Digital Applications

This paper describes a CMOS building block dedicated to high performance mixed analog-digital circuits and systems. The circuit consists of six MOS transistors realizing a new wideband and tunable transconductance. The theory of operation of this device is presented and the effects of transistor nonidealities on the global performances are investigated. Use of the proposed circuit to realize tunable functions (Gm-C filter and current opamp) is illustrated. HSPICE simulations show a wide tuning range of the transconductance value from 40 μS to 950 μS (500 μS) for ±2.5 V (±1.5 V) supply voltages. The transconductance value remains constant up to frequencies beyond 500 MHz. The bandpass filter built with few transconductance blocks and capacitances was simulated with ±2.5 V supply voltage, the center frequency is tunable in the range of 30 MHz to 110 MHz. However, the opamp, which is designed with a transresistance-transconductance architecture, was simulated with ±1.5 V supply voltage. The gain of the opamp can be tuned between 70 dB and 96 dB and high gain-bandwidth product of 145 MHz has been achieved at power consumption of less than 0.5 mW. Experimental results on a fabricated transconductor chip are provided.

Resonant-cavity separate absorption, charge and multiplication avalanche photodiodes with high-speed and high gain-bandwidth product

Previously, it has been shown that resonant-cavity separate-absorption-and-multiplication (SAM) avalanche photodiodes (APD's) exhibit high-speed and high gain-bandwidth products. In this letter, we describe a resonant-cavity SAM APD with an additional charge layer that provides better control of the electric field profile. These devices have achieved bandwidths as high as 33 GHz in the low-gain regime and a record gain-bandwidth product of 290 GHz. We also describe the correlation between the gain-bandwidth product and the doping level in the charge layer. With width dependent ionization coefficients, the current versus voltage (I-V) and gain-bandwidth simulations agree well with the measured results and indicate that even higher gain-bandwidth should be achievable with an optimized SACM APD structure.

Performance of thin separate absorption, charge, and multiplication avalanche photodiodes

Previously, it has been demonstrated that resonant-cavity-enhanced separate-absorption-and-multiplication (SAM) avalanche photodiodes (APDs) can achieve high bandwidths and high gain-bandwidth products while maintaining good quantum efficiency. In this paper, we describe a GaAs-based resonant-cavity-enhanced SAM APD that utilizes a thin charge layer for improved control of the electric field profile. These devices have shown RC-limited bandwidths above 30 GHz at low gains and gain-bandwidth products as high as 290 GHz. In order to gain insight into the performance of these APDs, homojunction APDs with thin multiplication regions were studied. It was found that the gain and noise have a dependence on the width of the multiplication region that is not predicted by conventional models. Calculations using width-dependent ionization coefficients provide good fits to the measured results. These calculations indicate that the gain-bandwidth product depends strongly on the charge layer doping and on the multiplication layer thickness and, further, that even higher gain-bandwidth products can be achieved with optimized structures.