L.T. Tran

A 108-GHz InP-HBT monolithic push-push VCO with low phase noise and wide tuning bandwidth

This paper reports on what is believed to be the highest frequency bipolar voltage-controlled oscillator (VCO) monolithic microwave integrated circuit (MMIC) so far reported. The W-band VCO is based on a push-push oscillator topology, which employs InP HBT technology with peak f/sub T/s and f/sub max/s of 75 and 200 GHz, respectively. The W-band VCO produces a maximum oscillating frequency of 108 GHz and delivers an output power of +0.92 dBm into 50 /spl Omega/. The VCO also obtains a tuning bandwidth of 2.73 GHz or 2.6% using a monolithic varactor. A phase noise of -88 dBc/Hz and -109 dBc/Hz is achieved at 1- and 10-MHz offsets, respectively, and is believed to be the lowest phase noise reported for a monolithic W-band VCO. The push-push VCO design approach demonstrated in this work enables higher VCO frequency operation, lower noise performance, and smaller size, which is attractive for millimeter-wave frequency source applications.

Low phase noise millimeter-wave frequency sources using InP-based HBT MMIC technology

A family of millimeter-wave sources based on InP heterojunction bipolar transistor (HBT) monolithic microwave/millimeter-wave integrated circuit (MMIC) technology has been developed. These sources include 40-GHz, 46-GHz, 62-GHz MMIC fundamental mode oscillators, and a 95-GHz frequency source module using a 23.8-GHz InP HBT MMIC dielectric resonator oscillator (DRO) in conjunction with a GaAs-based high electron mobility transistor (HEMT) MMIC frequency quadrupler and W-band output amplifiers. Good phase noise performance was achieved due to the low 1/f noise of the InP-based HBT devices. To our knowledge, this is the first demonstration of millimeter-wave sources using InP-based HBT MMICs.

Ultra-low dc power GaAs HBT S- and C-band low noise amplifiers for portable wireless applications

We report on a 2.1 mW low dc power GaAs HBT LNA with 2.0 dB noise figure and 8.9 dB gain at 2 GHz. This amplifier achieves a Gain/NF.P/sub dc/ ratio figure of merit of 2.10 (1/mW) which is the highest reported at S-band. Under low dc power bias of 2 V and 0.46 mA (0.92 mW), the amplifier achieves 5.2 dB gain, 3.01 dB noise figure and a Gain/P/sub dc/ figure of merit of 5.65 (dB/mW) which is also the highest reported in this frequency band. In addition, a 2-stage self-biased C-band LNA which achieves a minimum noise figure of 2.4 dB at 5 GHz, 16.2 dB gain, with only 72 mW of dc power was also demonstrated. This is believed to be the lowest noise figure performance so far reported for an HBT amplifier above 3 GHz. Both HBT LNAs are fabricated using a relaxed 3 /spl mu/m emitter width low cost GaAs production foundry process. The high performance obtained from HBTs at very low dc bias makes them attractive for portable wireless applications in the Industrial-Scientific-Medical (ISM) frequency bands.

High-reliability GaAs-AlGaAs HBTs by MBE with Be base doping and InGaAs emitter contacts

The authors have developed a modified MBE growth process to produce high-gain n-p-n GaAs-AlGaAs heterojunction bipolar transistors (HBTs) with a mean time to failure (MTTF) of 1.5*10/sup 8/ h at 125 degrees C. Beryllium incorporation and diffusion are controlled through a combination of reduced substrate temperature and increased As/Ga flux ratio during MBE growth, resulting in extremely stable HBT profiles. The authors also demonstrate graded InGaAs surface layers with nonalloyed refractory metal contacts that significantly improve ohmic reliability compared to alloyed AuGe contacts. The ability to produce robust HBTs by MBE is critically important to this technology.<<ETX>>

A 50-MHz-55-GHz multidecade InP-based HBT distributed amplifier

The authors report on a 50-MHz-55-GHz multidecade bandwidth InP-based heterojunction bipolar transistor (HBT) MMIC distributed amplifier (DA) which achieves the widest bandwidth and highest frequency of operation so far demonstrated for a bipolar amplifier. The HBT MMIC DA was fabricated using a high-speed 1-μm InAlAs-InGaAs-InP HBT base-undercut technology with peak fTs and fmaxs of 80 and 200 GHz, respectively, in order to obtain broad-band gain. Key to this work is the successful employment of HBT active load terminations used on both the input and output DA transmission lines in order to extend the low-frequency gain performance down to baseband. With only 82 mW of DC power consumption, the amplifier obtains measured gains of 7.6 dB at 50 MHz, 5.7 dB at 30 GHz, 5.8 dB at 50 GHz, and 3.1 dB at 55 GHz. Simulations of a monolithically integrated InGaAs p-i-n photodetector predicts a baseband 47-GHz photoreceiver response with an effective transimpedance of 38-dB/spl Omega/. The baseband millimeter-wave capability of the InP-based HBT DA and its compatibility with InGaAs photodetectors makes this technology attractive for future generation (>40 Gb/s) high-data-rate light-wave applications.

Reliability analysis of GaAs/AlGaAs HBTs under forward current/temperature stress

The reliability of GaAs/AlGaAs heterojunction bipolar transistors is investigated by accelerated life-testing of discrete devices under forward bias stress at elevated temperatures. The DC device characteristics are monitored to evaluate the effect of bias/temperature stress on a large number of devices fabricated on MBE (molecular beam epitaxy) grown material. The primary degradation observed in some devices is a reduction in the current gain which appears to be due to an electric field-aided diffusion of interstitial Be from the base into the base-emitter graded region. Other devices with optimal epitaxial material show stable current gain after DC bias stress at high temperature. Ohmic contact degradation, with or without bias, is also observed at the emitter contact, resulting in an increased emitter series resistance.<<ETX>>

A 62-GHz monolithic InP-based HBT VCO

A monolithic V-band VCO using InP-based HBT technology has been designed, fabricated, and tested. This VCO delivers a peak output power of 4 dBm at a center frequency of 62.4 GHz with a tuning range of 300 MHz. The measured phase noise shows -78 dBc/Hz at 100 kHz offset and -104 dBc/Hz at 1 MHz offset. To our knowledge, this is the highest frequency fundamental-mode oscillator ever reported using bipolar transistors. >

GaAs HBT wideband matrix distributed and Darlington feedback amplifiers to 24 GHz

The designs and performances of a 2-24 GHz distributed matrix amplifier and 1-20 GHz 2-stage Darlington coupled amplifier based on an advanced HBT MBE profile that increases the bandwidth response of the distributed and Darlington amplifiers by providing lower base-emitter and collector-base capacitances are presented. The matrix amplifier has a 9.5 dB nominal gain and a 3-dB bandwidth to 24 GHz. This result benchmarks the highest bandwidth reported for an HBT distributed amplifier. The input and output VSWRs are less than 1.5:1 and 2.0:1, respectively. The total power consumed is less than 60 mW. The chip size measures 2.5*2.6 mm/sup 2/. The 2-stage Darlington amplifier has 7 dB gain and 3-dB bandwidth beyond 20 GHz. The input and output VSWRs are less than 1.5:1 and 2.3:1, respectively. This amplifier consumes 380 mW of power and has a chip size of 1.66*1.05 mm/sup 2/. >

A DC-20-GHz InP HBT balanced analog multiplier for high-data-rate direct-digital modulation and fiber-optic receiver applications

This paper reports on a dc-20-GHz InP heterojunction bipolar transistor (HBT) active mixer, which obtains the highest gain-bandwidth product (GBP) thus far reported for a direct-coupled analog mixer integrated circuit (IC). The InP HBT active mixer is based on the Gilbert transconductance multiplier cell and integrates RF, local oscillator, and IF amplifiers, High-speed 70-GHz f/sub T/ and 160-GHz f/sub max/ InP HBT devices along with microwave matching accounts for its record performance. Operated as a down-converter mixer, the monolithic microwave integrated circuit achieves an RF bandwidth (BW) from dc-20 GHz with 15.3-dB gain and benchmarks a factor of two improvement in GBP over state-of-the-art analog mixer ICs. Operated as an up-converter, direct-digital modulation of a 2.4-Gb/s 2/sup 31/ -1 pseudorandom bit sequence (PRBS) onto a 20-GHz carrier frequency resulted in a carrier rejection of a 28 dB, clock suppression of 35 dBc, and less than a 50-ps demodulated eye phase jitter. The analog multiplier was also operated as a variable gain amplifier, which obtained 20-dB gain with a BW from dc-18 GHz, an third-order intercept of 12 dBm, and over 25 dB of dynamic range. A single-ended peak-to-peak output voltage of 600 mV was obtained with a /spl plusmn/35-mV 15 Gb/s 2/sup 5/-1 PRES input demonstrating feasibility for OC-192 fiber-telecommunication data rates. The InP-based analog multiplier IC is an attractive building block for several wideband communications such as those employed in satellites, local multipoint distribution systems, high-speed local area networks, and fiber-optic links.

Extending the bandwidth performance of heterojunction bipolar transistor-based distributed amplifiers

An InAlAs-InGaAs-InP HBT CPW distributed amplifier (DA) with a 2-30 GHz 1-dB bandwidth has been demonstrated which benchmarks the widest bandwidth reported for an HBT DA. The DA combines a 100 GHz fmax and 60 GHz fT HBT technology with a cascode coplanar waveguide DA topology to achieve this record bandwidth. The cascode gain cell offers 5-7 dB more available gain (MAG) than a common-emitter, and is used to extend the amplifiers upper frequency performance. A coplanar waveguide design environment is used to simplify the modeling and fabrication, as well as to reduce the size of the amplifier. Novel active load terminations for extending the DAs lower frequency response were separately demonstrated. The active loads are capable of extending the lower bandwidth performance by two decades resulting in performance below 45 MHz. This work explores both design techniques and technology capability which can be applied to other distributively matched HBT circuits such as active baluns for mixers, active combiners/dividers, and low DC power-broadband amplifiers.