InP Heterojunction Bipolar Transistors Research Articles

In-band OSNR monitor with high-speed integrated Stokes polarimeter for polarization division multiplexed signal

An in-band optical signal-to-noise ratio (OSNR) monitor is proposed, based on an instantaneous polarization state distribution analysis. The proposed monitor is simple, and is applicable to polarization division multiplexed signals. We fabricate a high-speed Stokes polarimeter that integrates a planar lightwave circuit (PLC) based polarization filter, high-speed InP/InGaAs photodiodes and InP hetero-junction bipolar transistor (HBT) trans-impedance amplifiers (TIA). We carry out proof-of-concept experiments with the fabricated polarimeter, and successfully measure the OSNR dependent polarization distribution with 100-Gb/s dual polarization quadrature phase shift keying (DP-QPSK) signals.

Experimental and modelling investigation of the influence of noise transit time and self-heating on microwave noise of Si/SiGe:C and InP/InGaAs HBTs

The results of a comprehensive experimental and modelling investigation of high-frequency noise (HFN) of Si/SiGe:C and InP/InGaAs heterojunction bipolar transistors (HBTs) demonstrate that the key parameters to correctly model HFN for both HBTs are the self-heating (SH) effect at high collector injection levels, i.e. JC > 2–3 mA µm−2, and the noise transport time (τ) which must be included at all bias levels. In contrast, thermal noise contribution of the base–emitter junction of the Si/SiGe:C HBT, associated with the diffusive nature of electron transport at this junction because of the lack of conduction band discontinuity, is only important at operation frequencies lying in the frequency range f > fT/2. The noise analysis indicates that in order to correctly model HFN performances at any injection level and operation frequency, τ must be constant with bias and equal to the addition of base and collector transit times (τB + τC). On the other hand, at high JC levels if SH is neglected, then the amplitude of the equivalent noise resistance (Rn) will be the most impacted noise parameter for both HBTs. Concerning the InP/InGaAs HBT, if SH is off at JC = 5.5 mA µm−2, the minimum noise figure (NFmin) of the InP HBT will be underestimated by 10%.

InP HBT Transferred to Higher Thermal Conductivity Substrate

We report the first demonstration of an InP double heterojunction bipolar transistor (HBT) transferred to a higher thermal conductivity substrate. This process allows lithographic access to both the frontside and backside of the device to minimize parasitic capacitances while transfer to a SiC substrate should reduce junction temperature by 42%, allowing for higher current density operation. The 0.20 × 3 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> emitter-area HBT has peak common-emitter current gain β = 22 and breakdown V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> , <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CEO</sub> >; 4 V. No electrical degradation from the transferred-substrate process is observed. RF measurements show device peak <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">τ</sub> = 397 GHz, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ≥ 400 GHz, and maximum available gain (MAG) at 100 GHz is 15.3 dB.

Passivation of InP heterojunction bipolar transistors by strain controlled plasma assisted electron beam evaporated hafnium oxide

We present structural, stress, and electrical properties of plasma assisted e-beam evaporated hafnium dioxide (HfO2) layers on n-type InP substrates. These layers have subsequently been used for surface passivation of InGaAs/InP heterostructure bipolar transistors either alone or in combination with plasma enhanced chemical vapor deposited SiO2 layers. The use of stacked HfO2/SiO2 results in better interface quality with InGaAs/InP heterostructures, as illustrated by smaller leakage current and improved breakdown voltage. These improvements can be attributed to the reduced defect density and charge trapping at the dielectric-semiconductor interface. The deposition at room temperature makes these films suitable for sensitive devices.

Ultrahigh-Speed Low-Power DACs Using InP HBTs for Beyond-100-Gb/s/ch Optical Transmission Systems

This paper presents the circuit designs and measured performance of two ultrahigh-speed low-power 6-b digital-to-analog converters (DACs) using InP-based heterojunction bipolar transistors (HBTs) for beyond-100-Gb/s/ch optical transmission systems. The first design is based on an R-2R ladder-based current-steering architecture with a novel double-sampling technique that relaxes the speed restraints for the DAC and helps achieve ultrahigh-speed operation. The DAC with the double-sampling technique achieves an excellent sampling speed of up to 32 GS/s with low power consumption of 1.4 W. The second design is based on a new timing alignment technique. The DAC with the timing alignment technique operates at a sampling rate of 28 GS/s with very low power consumption of 0.95 W and achieves an excellent figure of merit (0.53 pJ per conversion step). It provides a clear multilevel modulated signal for QAM transmission and can be applied to beyond-100-Gb/s/ch optical transmission systems.

235 GHz Amplifier Using 150 nm InP HBT High Power Density Transistor

In this letter, a four-stage 235 GHz heterojunction bipolar transistor (HBT) amplifier is reported. Each stage uses a single-emitter 0.15 × 3 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> InP HBT with collector current density of 25 mA/μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , maximum frequency of oscillation ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) greater than 500 GHz, and a cutoff frequency ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fT</i> ) of 320 GHz. The MMIC amplifier is realized in inverted microstrip topology. The amplifier demonstrates measured small signal gain of 12.7 dB and output power of 2.6 mW with a power gain of 9.4 dB. This corresponds to transistor output power density of 5.7 mW/μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 235 GHz. This is the highest HBT transistor output power density published to date at frequencies above 170 GHz, which indicates high power InP HBT power amplifiers should be viable with on-chip power combining.

0.25-µm-Emitter InP Heterojunction Bipolar Transistors with a Thin Ledge Structure

This paper describes 0.25-µm-emitter InP heterojunction bipolar transistors (HBTs) with a thin ledge structure. The HBTs consist of a degenerately-doped n+-InGaAs/15-nm-thick undoped InP emitter, a 25-nm-thick p+-In0.53Ga0.47As base, and a 75-nm-thick In0.53Ga0.47As collector. The emitter enables fabrication of a 15-nm-thick ledge structure simply by wet etching the n+-InGaAs emitter. The emitter mesa and base metal were scaled down to 0.25 and 0.3 µm, respectively. The fabricated HBT with a 0.25-µm emitter provides a current gain of 62 at a collector current density, Jc, of 10 mA/µm2. With the thin ledge structure, the current gain is virtually independent of emitter size and emitter–base spacing. The HBT also exhibits an ft of 442 GHz and an fmax of 214 GHz at a Jc of 12 mA/µm2. The results of bias-temperature stress tests show that base and collector currents are stable up to 1042 h at a Jc of 5 mA/µm2.

InP/InGaAs heterojunction bipolar transistors with different μ-bridge structures

Several μ-bridge structures for InP-based heterojunction bipolar transistors (HBTs) are reported. The radio frequency measurement results of these InP HBTs are compared with each other. The comparison shows that μ-bridge structures reduce the parasites and double μ-bridge structures have a better effect. Due to the utilization of the double μ-bridges, both the cutoff frequency fT and also the maximum oscillation frequency fmax of the 2 × 12.5 μm2 InP/InGaAs HBT reach nearly 160 GHz. The results also show that the μ-bridge has a better effect in increasing the high frequency performance of a narrow emitter InP HBT.

Photoreflectance spectroscopy for the qualification of GaAsSb alloys introduced in ultrafast heterojunction bipolar transistors on InP

AbstractGaAsSb is an important III–V semiconductor ternary alloy which is currently used as the thin base layer in high speed InP Heterojunction Bipolar Transistors (HBT). Up to now, very little is known about physical properties of GaAsSb alloys, such as surface Fermi level pinning and Schottky barrier heights with different contact metals. However such parameters impact directly the cut‐off frequency of HBT devices. Photoreflectance spectroscopy is applied to specific samples differing by their Sb concentration. The exploitation of Franz–Keldysh Oscillations (FKO) spectra allows determining the Fermi level pinning at the free surface of GaAsSb as a function of the alloy composition. Micro‐electroreflectance spectroscopy is also applied to Schottky diodes performed on the same structures, with Ti deposited at the GaAsSb surface. The Schottky barrier height between GaAsSb and Ti is derived from the FKO system recorded in the micro‐electroreflectance spectra. (© 2009 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

40 ns pulsed I/V setup and measurement method applied to InP HBT characterisation

A new technique and setup that enable pulsed I/V measurements of heterojunction bipolar transistors (HBTs) using very narrow 40 ns pulse widths is proposed. The characterisation methodology consists in driving the transistor base with constant direct current (DC current) while applying pulsed collector-emitter voltages (V ce ). The V ce quiescent value is set to 0V. The V ce pulse peak is monitored to scan the I c /V ce network. InGaAs/InP HBTs from Alcatel Thales III-V Lab have been measured for pulse widths varying from 300 down to 40 ns. The reported measurement results highlight the potential advantages of the proposed technique for transistor electro-thermal characterisation and modelling.

A physical-model of small-signal InP-based double heterojunction bipolar transistors and its parameter extraction technique

The influence on the base-collector junction capacitance Cbc of the energy band structure of the InP heterojunction bipolar transistors is researched. A physical model of small-signal InP double heterojunction bipolar transistor （DHBT） is developed, which takes into account the base-emitter and collector-emitter metalisations by using two additional capacitances Cmb and Cmc. The resistance of the model is divided into the intrinsic resistance, the extrinsic resistance and the parasitic resistance. Meanwhile, a physically meaningful small-signal parameter extraction procedure for the model is presented, in which all the equivalent circuit elements are extracted without reference to numerical optimization. An experimental validation is carried out, and excellent results are obtained over a wide range of bias points, which demonstrates good modeling accuracy.

30 Gb/s Over 100-m MMFs Using 1.1-$\mu$m Range VCSELs and Photodiodes

We developed 1.1-mum-range vertical-cavity surface-emitting lasers based on InGaAs-GaAs quantum wells, back-illuminated InGaAs photodiodes, and transimpedance amplifiers (InP heterojunction bipolar transistor) for high-speed optical interconnection. Clear eye opening operation and error-free transmission at 30 Gb/s over 100-m multimode fibers (GI32) were successfully achieved for the first time.

Demonstration of 184 and 255-GHz Amplifiers Using InP HBT Technology

In this letter, 184 and 255 GHz single-stage heterojunction bipolar transistor (HBT) amplifiers are reported. Each amplifier uses a single-emitter 0.4 ¿m 15 ¿m InP HBT device with maximum frequency of oscillation (f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> ) greater than 500 GHz and of 200 GHz. The 183 GHz single-stage amplifier has demonstrated gain of 4.3 ± 0.4 dB for all sites on the wafer. The 255 GHz amplifier has measured gain of 3.5d B and demonstrates the highest frequency measured HBT amplifier gain reported to date. Both amplifiers show excellent agreement with original simulation.

Integrated Heterojunction Bipolar Transistor Optically Injection-Locked Self-Oscillating Opto-Electronic Mixers for Bi-Directional Fiber-Fed Wireless Applications

A 30-GHz-band third harmonic optically injection-locked self-oscillating opto-electronic mixer is implemented with a 10-GHz InP heterojunction bipolar transistor monolithic microwave integrated circuit oscillator. The monolithic self-oscillating mixer can be optically injection locked in wide operating conditions and can perform efficient frequency up- and down-conversion with low-power optical local-oscillator signals. Using the mixer, bi-directional transmission of 32 quadrature amplitude modulation data in a 30-GHz fiber-fed wireless link is successfully demonstrated.

Microphotoreflectance spectroscopy of heterojunction bipolar transistors under biasing voltage: Measurement of the net doping concentration

The authors present a microphotoreflectance (micro-PR) spectroscopic study of a biased InGaAlAs∕GaAsSb∕InP heterojunction bipolar transistor. Franz Keldysh oscillations from an InGaAlAs emitter are studied as a function of the static biasing voltage applied to the emitter-base junction. The electric field value from the InGaAlAs emitter is decreasing under direct biasing voltage. The change in electric field value is shown to be in good agreement within the expected operation of forward biased junction, and making possible a straight measurement of the net doping concentration. Results show the feasibility of a micro-PR spectroscopy analysis of devices under operation.

Investigation Into the Scalability of Selectively Implanted Buried Subcollector (SIBS) for Submicrometer InP DHBTs

Recent attempts to achieve 400 GHz or higher f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> with InP heterojunction bipolar transistors (HBTs) have resulted in aggressive scaling into the deep submicrometer regime. In order to alleviate some of the traditional mesa scaling rules, several groups have explored selectively implanted buried subcollectors (SIBS) as a means to decouple the intrinsic and extrinsic collector design. This allows tau <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> to be minimized without incurring a large total C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BC</sub> increase, and hence, a net improvement in f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T </sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> is achieved. This paper represents the first investigation into the series resistance and capacitance characteristics of submicrometer-width SIBS regions (as narrow as 350 nm) for InP double HBTs. Although the SIBS resistance is higher than that of epitaxially grown layers, the SIBS concept is able to provide good dopant activation and a significant decrease in C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BC</sub> . S-parameter measurements are presented to clarify the impact of SIBS geometry variations, caused by both intentional device design and process variations, on f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T </sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> . Parasitic resistances and high background doping limit the f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> improvement, but the C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BC</sub> reduction is sufficient to demonstrate a 30% increase in f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> . Results indicate that further improvements in f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T </sub> and f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">MAX</sub> using the SIBS concept will be possible

High-Speed Uni-Traveling-Carrier Photodiodes Monolithically Integrated with InP Heterojunction Bipolar Transistors using Be Ion Implantation

Uni-traveling-carrier photodiodes (UTC-PDs) can be monolithically integrated with InP heterojunction bipolar transistors (HBTs) using Be ion implantation and rapid thermal annealing (RTA) for an activation of implanted Be. UTC-PDs share the base and collector layers of the HBTs; the photoabsorption layer of the UTC-PD is formed by selectively doping the collector with Be. The fabricated UTC-PDs exhibit an output voltage of over 0.5 V and a 3-dB bandwidth of 100 GHz. The HBTs fabricated on the same wafer provide a peak ft of 150 GHz and a peak fmax of 250 GHz at a collector current density of 1 mA/µm2. The RTA used to fabricate the UTC-PDs does not seriously degrade the current gain of the HBTs. These results indicate that Be ion implantation is a promising technique for integrating UTC-PDs and InP HBTs on the same wafer.

75 GHz InP HBT distributed amplifier with record figures of merit and low power dissipation

We present an InP heterojunction bipolar transistor (HBT) distributed amplifier with a bandwidth of 75 GHz, gain of 14 dB, and a record low power consumption of 78 mW. The HBTs had a 600-nm-thick collector, and hence a relatively low f/sub T/ and f/sub max/ of 84 and 150 GHz, respectively. The thick collector is a tradeoff required in optoelectronic integrated receivers, in which the PIN diode layers are the same as the base collector layers. To obtain high PIN diode responsivity, the collector layer needs to be thicker than in optimized HBTs. The amplifier topology comprises an emitter follower at the input and a cascode stage, with a resistor and inductance at the emitter follower output, and a peaking line between the HBTs in the cascode stage. The amplifier exhibits matching at the input better than -10 dB up to 85 GHz. The chip contains 16 HBTs and its size is 1.7/spl times/0.9 mm/sup 2/.

An approach to determine small-signal model parameters for InP-based heterojunction bipolar transistors

A new method for the extraction of the small-signal model parameters of InP-based heterojunction bipolar transistors (HBT) is proposed. The approach is based on the combination of the analytical and optimization technology. The initial values of the parasitic pad capacitances are extracted by using a set of closed-form expressions derived from cutoff mode S-parameters without any test structure, and the intrinsic elements determined by using the analytical method are described as functions of the parasitic elements. An advanced design system is then used to optimize only the parasitic parameters with very small dispersion of initial values. Good agreement is obtained between simulated and measured results for an InP HBT with 5/spl times/5 /spl mu/m/sup 2/ emitter area over a wide range of bias points up to 40 GHz.

Characterization of InP/InGaAs Heterojunction Bipolar Transistors with Carbon-Doped Base Layers Grown by Metal-Organic Chemical Vapor Deposition and Molecular Beam Epitaxy

We characterized InP/InGaAs heterojunction bipolar transistors (HBTs) with carbon-doped InGaAs base layers grown by metal-organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). Since HBTs grown using these techniques require different processing steps, resulting in different types of process-related damage, we analyzed the bulk and periphery components of DC characteristics to clarify the effects of the crystal growth and process techniques on device characteristics separately. The MBE-grown HBTs were found to have an advantage over the MOCVD-grown HBTs, because they do not require harmful high-temperature annealing during processing steps. On the other hand, it was also shown that the MOCVD-grown HBTs have a significantly lower base recombination rate than the MBE-grown HBTs, making MOCVD a suitable method of growing InP HBTs that do not require annealing, such as that with a GaAsSb base.