A.K. Oki

GaAs heterojunction bipolar transistor device and IC technology for high-performance analog and microwave applications

GaAs-AlGaAs n-p-n heterojunction bipolar transistor (GaAs HBT) technology and its application to analog and microwave functions for high-performance military and commercial systems are discussed. In many applications the GaAs HBT offers key advantages over the alternative advanced silicon bipolar and III-V compound field-effect-transistor (FET) approaches. TRWs GaAs HBT device and IC fabrication process, basic HBT DC and RF performance, examples of applications, and technology qualification work are presented and serve as a basis for addressing general capability issues. A related 3- mu m emitter-up, self-aligned HBT IC process provides excellent DC and RF performance, with simultaneous gain-bandwidth product, f/sub T/, and maximum frequency of oscillation, f/sub max/, of approximately 20-40 GHz and DC current gain beta approximately=50-100 at useful collector current densities approximately=3-10 kA/cm/sup 2/, early voltage approximately=500-1000 V, and MSI-LSI integration levels. These capabilities facilitate versatile DC-20-GHz analog/microwave as well as 3-6 Gb/s digital applications, 2-3 G sample/s A/D conversion, and single-chip multifunctions with producibility. >

A 6-GHz integrated phase-locked loop using AlGaAs/GaAs heterojunction bipolar transistors

A fully integrated 6-GHz phase-locked-loop (PLL) fabricated using AlGaAs/GaAs heterojunction bipolar transistors (HBTs) is described. The PLL is intended for use in multigigabit-per-second clock recovery circuits for fiber-optic communication systems. The PLL circuit consists of a frequency quadrupling ring voltage-controlled oscillator (VCO), a balanced phase detector, and a lag-lead loop filter. The closed-loop bandwidth is approximately 150 MHz. The tracking range was measured to be greater than 750 MHz at zero steady-state phase error. The nonaided acquisition range is approximately 300 MHz. This circuit is the first monolithic HBT PLL and is the fastest yet reported using a digital output VCO. The minimum emitter area was 3 mu m*10 mu m with f/sub t/=22 GHz and f/sub max/=30 GHz for a bias current of 2 mA. The speed of the PLL can be doubled by using 1- mu m*10- mu m emitters in next-generation circuits. The chip occupies a die area of 2-mm*3-mm and dissipates 800 mW with a supply voltage of -8 V. >

Ultra high speed direct digital synthesizer using InP DHBT technology

Direct Digital Synthesizers (DDS) offer advantages such as precise beam shaping and forming over conventional RF approaches. This paper discusses novel design and process techniques that enable direct digital synthesis of S-band output frequencies using our current InP double-heterojunction bipolar transistor (DHBT) technology with a cantilevered base layer and undercut collector. The test results demonstrate a DDS chip operating at the world record clock rate of 9.2 GHz. Further design and process improvements will be implemented in future generation circuits that will enable synthesis of Ku-band frequencies.

A novel HBT distributed amplifier design topology based on attenuation compensation techniques

We report on a novel HBT distributed amplifier design which achieves the highest gain-bandwidth product (GBP) per device f/sub T/ so far reported for HBT distributed amplifiers. This paper introduces a new design topology for HBT DAs which incorporates attenuation compensation on both the input and output transmission lines. A four-section HBT DA using this novel topology achieves a gain of 15 dB and a 3-dB bandwidth of >15 GHz. The resulting gain-bandwidth product is 84 GHz. When normalized to the device f/sub T/, this DA achieves the highest normalized gain-bandwidth-product figure of merit for HBT DAs, /spl ap/3.67, which is a 55% improvement over existing state-of-the-art performance. Attenuation compensation of the input transmission line is realized using HBT active impedance transformations. The resulting transistor configuration consists of a common-collector driving a common-emitter-cascode transistor pair. This configuration offers 15-20 dB more available gain for the device unit cell, and results in gain-bandwidth product improvements of 200% over a conventional common-emitter DA configuration. This paper discusses the design theory, techniques, and measurements of this newly developed HBT distributed amplifier topology. >

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>>

Monolithic HEMT-HBT integration by selective MBE

We have achieved successful monolithic integration of high electron mobility transistors and heterojunction bipolar transistors in the same microwave circuit. We have used selective molecular beam epitaxy and a novel merged processing technology to fabricate monolithic microwave integrated circuits that incorporate both 0.2 /spl mu/m gate-length pseudomorphic InGaAs-GaAs HEMTs and 2 /spl mu/m emitter-width GaAs-AlGaAs HBTs. The HEMT and HBT devices produced by selective MBE and fabricated using our merged HEMT-HBT process exhibited performance equivalent to devices fabricated using normal MBE and our baseline single-technology processes. The selective MBE process yielded 0.2 /spl mu/m HEMT devices with g/sub m/=600 mS/mm and f/sub T/=70 GHz, while 2/spl times/10 /spl mu/m/sup 2/ HBT devices achieved /spl beta/>50 and f/sub T/=21.4 GHz at J/sub c/=2/spl times/10/sup 4/ A/cm/sup 2/. The performance of both a 5-10 GHz HEMT LNA with active on-chip HBT regulation and a 20 GHz Darlington HBT amplifier are shown to be equivalent whether fabricated using normal or selective MBE. >

12-40 GHz low harmonic distortion and phase noise performance of GaAs heterojunction bipolar transistors

GaAs-AlGaAs heterojunction bipolar transistors (HBTs) have been used to demonstrate the capability of low harmonic distortion with high efficiency and low-phase-noise performance in the 12-40-GHz frequency regime. A simplified 3- mu m emitter, self-aligned base metal HBT process is used to fabricate transistors with f/sub max/ approximately=30-50 GHz, high linearity, and low 1/f noise, yielding significantly improved third-order intermodulation product intercept point (IP3) and oscillator performance. The HBT IP3 ranges from 20-35 dBm for 12-20 GHz with a linearity figure-of-merit ratio, IP3(mW)/input DC power (mW), approximately=4 to 20 times higher than comparable HEMTs (high-electron-mobility transistors) and MESFETs at 12 to 37.7 GHz with -82 dBc/Hz phase noise at 100-kHz offset. It is concluded that these capabilities make HBTs attractive for high-IP3 amplifiers and mixers and low-phase-noise voltage-controlled oscillators in advanced receiver applications.<<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.