A millimeter-wave monolithic integrated circuit power amplifier operating in the frequency range between 186 and 212 GHz is presented. The amplifier, dedicated to high-resolution imaging radar and communication systems, is realized in a 100 nm gate length metamorphic high electron mobility transistor technology. The three-stage design with four parallel transistors in the output stage achieves a linear gain of more than 12 dB and provides a saturated output power of more than 9 dBm and 7 dBm at 192 and 200 GHz, respectively

Kallfass, I.

Koch, S.

Leuther, A.

Massler, H.

Pahl, P.

Tessmann, A.

Zwick, T.

English

KITopen

410 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 19, NO. 6, JUNE 2009A 200 GHz Monolithic Integrated Power Amplifierin Metamorphic HEMT TechnologyI. Kallfass, P. Pahl, H. Massler, A. Leuther, A. Tessmann, S. Koch, and T. ZwickAbstract—A millimeter-wave monolithic integrated circuitpower amplifier operating in the frequency range between 186and 212 GHz is presented. The amplifier, dedicated to high-reso-lution imaging radar and communication systems, is realized in a100 nm gate length metamorphic high electron mobility transistortechnology. The three-stage design with four parallel transistorsin the output stage achieves a linear gain of more than 12 dB andprovides a saturated output power of more than 9 dBm and 7 dBmat 192 and 200 GHz, respectively.Index Terms—G-band, mHEMT, millimeter-wave field effecttransistor (FET) integrated circuits (ICs), millimeter-wave poweramplification, monolithic microwave integrated circuits (MMICs).I. INTRODUCTIONA midst today’s technologies covering the millimeter-wave(30–300 GHz) frequency range with its applications in re-mote sensing and communication, the millimeter-wave mono-lithic integrated circuit (MMIC) offers tremendous advantagesin terms of compactness, performance competitiveness as wellas ease-of-integration and deployment. The need for high powerlevels arises predominantly in the transmission paths of activesystems, e. g. in high resolution imaging radar and high datarate wireless communication, where operating range is a di-rect function of the transmit power. In passive systems, hetero-dyne receivers require high local oscillator power levels to drivetheir mixers. While MMIC technology has been shown to be ca-pable of providing low-noise amplifiers covering the entire mil-limeter-wave range [1], [2], relatively few works have been re-ported on MMIC-based power amplification beyond 100 GHz.In [3], Northrop Grumman Corp. (NGC) demonstrated a poweramplifier MMIC based on 70 nm InP high electron mobilityManuscript received October 16, 2008; revised February 27, 2009. Firstpublished May 26, 2009; current version published June 05, 2009. This workwas supported by Sony Deutschland GmbH Sensing Systems Laboratory, theGerman Federal Ministry of Defence (BMVg), and the Bundeswehr TechnicalCenter for Information Technology and Electronics (WTD81).I. Kallfass, H. Massler, A. Leuther, and A. Tessmann are with the FraunhoferInstitute for Applied Solid-State Physics (IAF), Freiburg D-79108, Germany(e-mail: ingmar.kallfass@iaf.fraunhofer.de).P. Pahl was with the Fraunhofer Institute for Applied Solid-State Physics(IAF), Freiburg D-79108, Germany and is now with the University of Karlsruhe(TH), Karlsruhe D-7613, Germany.S. Koch is with Sony Deutschland GmbH Sensing Systems Laboratory,Stuttgart D-70327, Germany.T. Zwick is with the University of Karlsruhe (TH), Karlsruhe D-7613, Ger-many.Color versions of one or more of the figures in this letter are available onlineat http://ieeexplore.ieee.org.Digital Object Identifier 10.1109/LMWC.2009.2020042transistor (HEMT) technology. This amplifier delivers a satu-rated output power of 13 dBm and 10 dBm up to 190 GHz whenoperated under a drain supply voltage of 2 V and 1.2 V, respec-tively. Entering the sub-millimeter-wave region, NGC recentlyreported 3 dBm of output power from a three-stage amplifier at330 GHz [4]. Based on InP double hetero-junction bipolar tran-sistor technology (DHBT) with its high breakdown voltages, a176 GHz amplifier with 9.1 dBm saturated output power hasbeen realized [5]. In this letter, we report a three-stage poweramplifier MMIC based on a 100 nm metamorphic HEMT tech-nology, achieving an output power of 9 dBm and 7 dBm at 192and 200 GHz, respectively.II. MHEMT TECHNOLOGYThe HEMT based on InGaAs/InAlAs hetero-structures withhigh In-content in the electron transport channel can be growneither pseudomorphic on InP wafers or by using a metamor-phic buffer to adapt the lattice constant on GaAs substrates.Major advantages of the metamorphic approach are cost andquality of the GaAs wafers as well as ease of wafer handling.Disadvantages of the metamorphic HEMT (mHEMT) are thelower thermal conductivity of the metamorphic buffer as wellas the additional growth effort. Based on the metamorphic ap-proach, the Fraunhofer Institute for Applied Solid State Physics(IAF) develops advanced MMIC processes including HEMTswith gate lengths from 100 nm down to 30 nm. Up to an op-erating frequency of 200 GHz and for power applications, the100 nm variant is the most appropriate choice. It features max-imum cutoff frequencies of 220 GHz and of 300 GHz.On- and off-state breakdown voltages are evaluated to 3.0 V and4.3 V, respectively [6].The mHEMT layers are grown on 4-inch semi-insulatingGaAs wafers by molecular beam epitaxy (MBE). For the meta-morphic buffer a lineartransition is used. For the 100 nm gate length technology theelectrons are confined in ancomposite channel to increase the breakdown voltages. The lowenergy electrons with high electron mobility are confined in thelayer. Additionally, the high energy electronsare distributed over both layers, which reduces impact ioniza-tion. The split channel is confined by barriers.The upper barrier layer includes a silicon -doping. The layersequence was capped with a highly doped layerto reduce the ohmic contact and source resistance. The 100 nmT-gates are defined by a 100 kV electron beam lithographyusing a three-layer resist. A Pt-Ti-Pt-Au layer sequence wasused for the gate metallization. The devices are passivatedwith a 250 nm thick CVD deposited SiN layer, which was1531-1309/$25.00 © 2009 IEEEAuthorized licensed use limited to: Karlsruhe Institute of Technology. Downloaded on March 09,2010 at 07:53:08 EST from IEEE Xplore.  Restrictions apply. First published in: EVA-STAR (Elektronisches Volltextarchiv – Scientific Articles Repository) http://digbib.ubka.uni-karlsruhe.de/volltexte/1000016495 KALLFASS et al.: 200 GHz MONOLITHIC INTEGRATED PA IN METAMORPHIC HEMT TECHNOLOGY 411Fig. 1. Circuit schematic of the three-stage power amplifier MMIC.also used as dielectric layer for the MIM capacitors. Furtherpassive elements are NiCr thin film resistors, an electron beamevaporated Au based interconnection layer, and a 2.7 thickplated Au layer in airbridge technology.For the realization of MMICs operating at frequencies beyond60 GHz the frontside process is extended by a full backside met-allization process, including wafer thinning to 50 substratethickness and via hole etching for increased rejection of para-sitic substrate modes in the coplanar transmission line environ-ment.III. AMPLIFIER DESIGNThe circuit schematic of the power amplifier is shown in Fig.1. A three-stage topology is adopted, with the first, second andthird stage employing one, two and four common-source tran-sistors in parallel, respectively.The individual transistors use four gate fingers with 10width each, i.e. devices. The transistor size is chosenfor maximum size in order to maximize the output power, whilemaintaining a reasonable small-signal gain of the overall ampli-fier of at least 10 dB at 200 GHz. The power splitter and com-biner networks in front of and after the transistors also serveas matching networks to achieve a 50 interface impedanceat every stage’s in- and output. The matching networks are de-signed for maximum gain. Load-pull simulations with large-signal models indicate that further improvement in output poweris possible by choosing the appropriate load impedance for max-imum output power. The validation of the large-signal model iscurrently under way.It is questionable whether the parallelization of transistorsis a practicable way for realizing power amplifiers at highmillimeter-wave frequencies. The loss incurred by the com-bining/splitting networks opposes the achievable gain andoutput power. Our simulations indicate a power loss of approx-imately 1.2 dB per combiner/splitter network in the frequencyrange from 180 to 210 GHz. The parallelization of four transis-tors in the output stage therefore results in a 3.6 dB increase ofthe output power from a single transistor. This is paid for bya reduced efficiency, since the DC power consumption scaleslinearly with the number of parallel transistors.Shunt resistors at the transistor gate and drain terminals areemployed for odd-mode suppression and to ensure stability inparallel amplifier branches. The gate and drain bias voltages aresupplied via lines before and after the power splitter/com-biner networks.Fig. 2 shows the chip photograph of the amplifier MMIC, im-plemented in a coplanar transmission line environment. Its totalchip size is . The gate and drain supply voltages areFig. 2. Chip photograph of the power amplifier MMIC realized in IAF 100 nmmetamorphic HEMT technology.Fig. 3. G-band S-parameter measurement of the 200 GHz power amplifierMMIC.provided for each stage individually for ease of testing. Specialcare is taken in the design of the RF shunt capacitance networksto ensure low-frequency stability of the circuit. This is achievedby a deliberate reduction of the shunt capacitors’ quality factor.IV. AMPLIFIER PERFORMANCES-parameter measurements in G-band (140–220 GHz) showthe amplifier’s linear gain and power matching characteristics.Fig. 3 shows the measured reflection and transmission coeffi-cients. A linear gain of 12.1 dB is achieved at 205 GHz. The3-dB bandwidth is 26 GHz (186–212 GHz, corresponding to arelative bandwidth of 13 %). The bias voltages at the drain andgate are set to and . Under these con-ditions, the amplifier consumes 160 mW of DC power and alltransistors operate at a current density of 409 mA/mm.Output power is measured on-wafer with all power levels nor-malized to the probe tip reference plane. In order to generateenough input power to drive the amplifier into saturation, a com-mercial diode-based frequency-doubler module is employed. Itcan generate up to 5 dBm of output power at the chip input ref-erence plane. The doubler is driven by an IAF power ampli-fier module delivering more than 100 mW output power up to110 GHz. The input signal to the power amplifier is generated bya W-band source module. The measurement setup is sketched inFig. 4.Fig. 5 shows the measurement results of output power andgain as a function of the input power at 192 and 200 GHz. Thebias conditions in the power measurement are as stated above.At 192 GHz the amplifier reaches a saturated output power of9.5 dBm when driven with 5 dBm input power. At 200 GHz,Authorized licensed use limited to: Karlsruhe Institute of Technology. Downloaded on March 09,2010 at 07:53:08 EST from IEEE Xplore.  Restrictions apply. 412 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 19, NO. 6, JUNE 2009Fig. 4. Output power measurement setup for 200 to 220 GHz.Fig. 5. Output power and gain versus input power at 192 GHz and 200 GHz.Fig. 6. Measurement of output power in a frequency sweep at constant inputpower levels.the output power saturates at 7.4 dBm with a gain of 4.4 dB. Theamplifier’s output-related 1-dB compression point is at 5.0 dBmand 3.1 dBm for 192 and 200 GHz, respectively.Within the measurement setup constraints, notably the band-width of the G-band frequency doubler, a sweep of the fre-quency was possible between 190 and 205 GHz. Fig. 6 showsthe amplifier output power for two different input power levels.Within the considered frequency range, no significant powerdegradation is observed.Table I shows a comparison of reported power amplifiers inthe frequency range from 150 to 300 GHz [7], [8].TABLE ICOMPARISON OF POWER AMPLIFIERS IN THE FREQUENCYRANGE FROM 150 TO 300 GHZV. CONCLUSIONThe 100 nm metamorphic HEMT technology, which wasoriginally developed and optimized for high cutoff frequencies,can be adopted for the implementation of power amplifierMMICs up to G-band frequencies. Combined with low-noiseamplifiers, frequency multipliers and mixers based on the sametechnology, fully MMIC-based high-performance analog fron-tends for active radar and communication systems operating inthe upper millimeter-wave region become feasible.ACKNOWLEDGMENTThe authors wish to thank their colleagues at the FraunhoferInstitute for Applied Solid-State Physics (IAF), for their excel-lent contributions during epitaxial growth and wafer processing,and M. Schlechtweg and O. Ambacher, for their continuous sup-port throughout this work.REFERENCES[1] W. R. Deal, X. B. Mei, V. Radisic, W. Yoshida, P. H. Liu, J. Uyeda, M.Barsky, T. Gaier, A. Fung, and R. Lai, “Demonstration of a S-MMICLNA with 16-dB gain at 340-GHz,” in Proc. IEEE Compound Semi-cond. Integr. Circuit Symp. CSICS, Portland, OR, Oct. 2007, pp. 75–78.[2] A. Tessmann, A. Leuther, H. Massler, W. Bronner, M. Schlechtweg,and G. Weimann, “Metamorphic H-band low-noise amplifier MMICs,”in IEEE MTT-S Int. Dig., Honolulu, HI, Jun. 2007, pp. 353–356.[3] P. Huang, R. Lai, R. Grundbacher, and B. Gorospe, “A 20-mW G-bandmonolithic driver amplifier using 0.07-um InP HEMT,” in IEEE MTT-SInt. Dig., San Francisco, CA, Jun. 2006, pp. 806–809.[4] W. R. Deal, X. B. Mei, V. Radisic, M. D. Lange, W. Yoshida, P. Liu, J.Uyeda, M. E. Barsky, A. Fung, T. Gaier, and R. Lai, “Development ofsub-millimeter-wave power amplifiers,” IEEE Trans. Microw. TheoryTech., vol. 55, no. 12, pp. 2719–2726, Dec. 2007.[5] V. K. Paidi, Z. Griffith, W. Yun, M. Dahlstrom, M. Urteaga, N.Parthasarathy, S. Munkyo, L. Samoska, A. Fung, and M. J. W. Rod-well, “G-band (140–220 GHz) and W-band (75–110 GHz) InP DHBTmedium power amplifiers,” IEEE Trans. Microw. Theory Tech., vol.53, no. 2, pp. 598–605, Feb. 2005.[6] A. Tessmann, “220-GHz metamorphic HEMT amplifier MMICs forhigh-resolution imaging applications,” IEEE J. Solid-State Circuits,vol. 40, no. 10, pp. 2070–2076, Oct. 2005.[7] W. R. Deal, X. B. Mei, V. Radisic, B. Bayuk, A. Fung, W. Yoshida, P.H. Liu, J. Uyeda, L. Samoska, T. Gaier, and R. Lai, “A new sub-mil-limeter wave power amplifier topology using large transistors,” IEEEMicrow. Wireless Compon. Lett., vol. 18, no. 8, pp. 542–544, Aug.2008.[8] W. R. Deal, X. B. Mei, V. Radisic, B. Bayuk, A. Fung, W. Yoshida,P. H. Liu, J. Uyeda, L. Samoska, T. Gaier, and R. Lai, “A balancedsub-millimeter wave power amplifier,” in IEEE MTT-S Int. Dig., Jun.2008, pp. 399–402.Authorized licensed use limited to: Karlsruhe Institute of Technology. Downloaded on March 09,2010 at 07:53:08 EST from IEEE Xplore.  Restrictions apply. 

A 200 GHz Monolithic Integrated Power Amplifier in Metamorphic HEMT Technology

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A 200 GHz monolithic integrated power amplifier in metamorphic HEMT technology

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A 200 GHz Monolithic Integrated Power Amplifier in Metamorphic HEMT Technology

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