0.1 gm In02Al0.8Sb-InAs HEMT Low-Noise Amplifiers forUltralow-Power Applications

Y. C. Chou, M. D. Lange, B. R. Bennett*, J. B. Boost, J. M. Yang, N. A. Papanicolaou*, C. H. Lin,L. J. Lee, P. S. Nam, A. L. Gutierrez, D. S. Farkas, R. S. Tsai, M. Wojtowicz, T. P. Chin, and A. K. Oki

Northrop Grumman Corporation, Redondo Beach, CA 90278Email: yeong-changchou@ ngc.com

* Naval Research Laboratory, Washington DC, 20375-5320

Abstract

A 0.1 tm Ino02Al08Sb-InAs HEMT MMIC technology was SiNxdeveloped for phased-array applications with ultralow-power =a=siatXiand oxidation-free requirements. An In0. 08Sb layer was as tutilized to replace the upper AlSb layer in the conventional / gltAlSb-InAs HEMT in order to mitigate the oxidation incurredby the AlSb layer. In this work, we have demonstratedexcellent dc and rf perforance on both devices and low-noise amplifiers (LNAs) using 0.1 tm In2A8lSb-InAs AAS mHEMTs on 3-inch GaAs substrates. This accomplishment is n-tISe InAs: Si dopedcrucial for phased-array applications with ultralow-power and AISboxidation-free requirements. InAs channel

AlSbIntroduction A Ga Sb buffer

AlSb-InAs HEMTs have proven to be a viable next- GaAs buffergeneration technology for low-noise, low-power, and high- GaAs substratespeed applications due to the superior electronic properties ofInAs, such as electron mobility and peak velocity. Theelectron mobility and peak velocity are nearly two times Fig. 1: Materials cross section of a conventional AlSb-InAs HEMTlarger than those of In052 Al048 As-nGal-,As-InP HEMTs with grown on a 3-inch GaAs substrate, in which highly reactive AlSb

In.Ga,As channels (1). The combination of high peak and strained In04A106As materials were used.

electron velocity (- 4xl07 cm/s) at low electric field and high high sheet charge density in the InAs channel. These inherentchannel conductivity enables operation of AlSb-InAs HEMTs g ylimitations in conventional AlSb-InAs HEMTs provide aat very low drain voltage. Accordingly, AlSb-InAs HEMTs strong incentive to develop a new material structure tohave become serious candidates for military and space mitigate oxidation and reduce access resistance to furtherapplications with ultralow-power requirements, such as enhance device reliability and performance.phased-array and satellite systems (2-5). Accordingly, new materials systems, such as InAs Sb -To assure the successful insertion of AlSb-InAs HEMT channel HEMTs (7), InAlSb-InAs HEMTs (8-9) and InSb-LNAs for military and space applications with ultra-low channel tIsTs (1), weredeveope To becom pntIal

powe reqireents reiabiityis esenial.Fig I sowschannel transistors (10), were developed to become potentialpower requirements, reliability is essential. Fig. 1 shows alternatives for replacing conventional AlSb-InAs HEMTs.

where AlSb is utilized in a conventional AlSb-InAs HEMT However donsratin ofvhighaperformance HEMT s

tecnolgy(6) Te hgh eativtyof he lS inAlb-IAs However, demonstration of high performance HEMT LNAstechnology (6). The high reactivity of the AlSb in AlSb-InAs using any of these new material structures was still lacking.HEMTs presents a challenge for preventing AlSb oxidation in thi or we he demonstrated exe le dckandrduring processing and/or dicing, particularly for AlSb layers pefomacwon bot devicstand LNAslusng 0.

am

* ° * 7 r- l * r- ~~~~performance on both devices and LNAs using 0.1 Rtmthicker than 500 A. During the processes of isolation etching In Al Sb-InAs HEMTs on 3-inch GaAs substrates. For theand dicing, the edges of the AlSb layers are exposed to air, 0.2 0.8risking oxidation and degradation of reliability performance. first time, LNAs of 0.1 m Ino A1 Sb-InAs HEMTs are

Additionally, the lattice mismatch of the relaxed In Al A demonstrated - with excellent rf performance while operating* ' ** * . ~~~~~~~.1*4 A061 at ultralow power (2 mW). This accomplishment is crucial forbarrier shown in Fig. 1, used to passivate the underlying AlSb

barrier in conventionalAl7b-InAs HEMTs is as high as phased-array applications with ultralow-power and oxidation-5.5%. As a result, it is difficult to grow a thick n+-doped InAs free requirements.cap layer to reduce the access resistance without the need for

1-4244-0439-X/07/$25.00 © 2007 IEEE 617

In 2Al 8Sb-InAs HEMT Technology Raw Data Simulation

The cross-section of a 0.1Im nO.2Al1.8Sb-lnAs UEMT is GaAs

shown in Fig. 2. The InO.2A10.8Sb-InAs HiEMT structure was 1OMgrown by molecular beam epitaxy (MBE) on 3-inch semi- 1insulating GaAs substrates. Silicon doping was used in our [i InAsstudy instead of Te (7-8). The excellent crystalline quality is InAISbsubstantiated by the x-ray rocking curve in Fig. 3, due to theIno.2Alo8Sb and InAs layers both remaining fully strained 0

despite the opposing 1.2% bulk-lattice mismatches between j Ieach of them and the Al07GaO3Sb buffer. Fig. 4 depicts the I

trend charts of room-temperature Hall channel-electronmobility Cue) and sheet concentration (fsheet), exhibiting

Fig. 3: X-ray rocking curves of In, 2Al08Sb-InAs HEMT materials,excellent repeatability. The typical tie iS at least 25,000 showing the high crystalline quality of the MBE-grown materials.cm2/V-s and often approaches 30,000 cm2/V-s, and nsheet isconsistently in the range of 1.0 ± 0.3 x 1012 cm2. In addition, 40 4atomic-force microscopy was used to characterize material lieroughness. The roughness over a 5x5 tm area is typically >30 * . * *0.7 nm, exhibiting excellent surface flatness of 1nO.2Al0.8Sb- 20InAs HEMT materials. l bSheet-A band diagram of the Ino2 0Alo Sb-InAs HEMT structure 10 ° ° 1shown in Fig. 5 was obtained using a calibrated densitygradient simulation (8). Both the Al07Gao3Sb and Ino2Alo Sb0layers provide a large conduction band offset with respect to Sequence of MBE Growth Runsthe InAs channel layer, thus allowing good confinement ofelectrons in the channel. Fig. 4: Trend charts of ug and nsht in Ino2Al08Sb-InAs HEMT materials.

The fabrication processes for Northrop Grumman' s (NG)AlSb-InAs HEMTs were reported previously (l1). The NGfabrication processes for In02 Al08Sb-InAs HEMTs are similarto those of AlSb-InAs HEMTs except for the new In02Al08Sb-InAs HEMT materials structure shown in Fig. 2. The devicemesa was formed by using a BCl3/Ar-based inductively-

SiNx coupled-plasma etching technique. The ohmic-contactpassivatin \resistance is as low as 0.06 *-mm. Electron-beam lithography

passivati\ was utilized to pattern gates with a length of 0.1 Inm. After T-

g\atb gate metal evaporation, devices were fully passivated by anitride layer deposited by a low-temperature, plasma-enhanced, chemical-vapor deposition (PECVD) technique.

InAs tact cap iiThis avoids increased gate leakage that would otherwise beI Inas LJ Lcontact cap Iinduced by high-temperature PECVD.

In-type InAs: Si doped 11.5_I In2AISbALL dopinglh61l c6} 11 SIInAs channel A1O7GaO3Sb| | W ~~~~~~~~~~~~~~~~~~0.50Al07GaO3Sb buffer

l~~~~~~~~~~~~~~~~~~~ ... .. .. .. ... .. .. .. ...... .. .. .. .. ..

GaAs bufferGaAs substrate 02AI _S

Fig. 2: Materials cross section of an In02A108Sb-InAs HEMT grown 0 5 10 15 20 25 30 35 40on a 3-inch GaAs substrate. In02Al08Sb layers were used to replace Position(nm)AlSb barrier layers of the conventional AlSb-InAs HEMT.

Fig. 5: A calculated band diagram of the Ino*2Alo*8Sb-InAs HEMT structure.

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In02Al08Sb-InAs HEMT Device Results 1400g VDS =0.3 V

The gate recess was performed with a wet-etching technique. E 1200Control of the gate-etch time is critical for achieving devices E

with low gate leakage. Scanning-transmission-electron 1000

microscopy (STEM) was utilized to study the gate-recess 800process in 1nO2Al08Sb-InAs HEMTs across a 3-inch GaAswafer. A representative gate-recess STEM micrograph is E 600shown in Fig. 6. The recess width is approximately 0.20-0.25 < /DS

gin. ~~~~~~~~~~~~~~~E400-Fig. 7 shows the distribution of drain current (IDS) and dc 20200-transconductance (gm) versus gate bias (VGs) of 0.1 tmIno2Al08Sb-InAs HEMTs across a 3-inch GaAs wafer. The 0.uniformity of dc performance is essential for good rf yield of -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0

LNAs. The average peak dc transconductance (gmp) is 1128 VGS (V)mS/mm at drain bias (VDS) = 0.3 V, with standard deviation of39 mS/mm; and the average drain current is 527 mA/mm at Fig 7: Distribution of IDS and g2 characteristics of 0.1 m

39 mS/mm;and the average drain current is 527 InAs HEMTs across a 3-inch GaAs substrate.VGS = 0 V, with standard deviation of 15 mA/mm. A typicaldc current-voltage (I-V) plot is shown in Fig. 8, exhibiting alow-field channel on resistance at VGS = 0 V of ___approximately 0.5 Q-mm. GS 500Fig. 9 shows the current-gain distribution versus VGStoP =O0Vfrequency of a 0.1 m 1no2Al08Sb-lnAs HEMT on a 3- 400 SV_bottom: -0.7 Vinch GaAs substrate. The extrapolated transistor cutoff p 0frequency (fT) is approximately 220 GHz on devices E 300biased at VDS = 0.3 V and VGS = -0.3 V on a 4x200g m aperiphery InO2Al0.8Sb-InAs HEMT, which is comparable Eto that of conventional AlSb-InAs HEMTs (11). - 200However, 1nO2Al08Sb-InAs HEMTs have no AlSb layer.Therefore, it is expected that the 1n0.2A10.8Sb-1nAs 100HEMTs are less vulnerable to oxidation. Consequently, itis believed that 1nO2Al08Sb-InAs HEMTs can become 0viable components for applications with ultralow-power 0 0.1 0.2 0.3and oxidation-free requirements. VDS (V)

Fig. 8: I- V characteristics of a 0.1 ,Im Ino.2A10.8Sb-InAs HEMT measured fromVGsof -0.7 V to 0 V with a step of 0.1 V.

100__

10 _ ____=__1 _ _ =_ __

_ 10Gate __

In ~ ~ ~~~~~~~~1 10 100 10001. *.

InO.2AI0.8Sb ~~~Fig. 9: Measured IH21 and extrapolated fT of a 4x200 jim peripherys

approximately 220 GHz fT which is comparable to that of conventionalFig. 6: A STEM micrograph of a 0.1 jim recessed Ino2A108Sb-InAs AlSb-InAs HEMTs. THEMT.

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Ino2Al 08Sb-InAs HEMT LNA Results Acknowledgement

The NG In0 2Al08Sb-InAs HEMT MMIC processes are This work was supported by DARPA under contract numberidentical to those of NG' s AlSb-InAs HEMT MMIC FA8750-06-C-005 1. The authors thank Dr. Mark Roskertechnology, including 300 pF/mm2 metal-insulator-metal (DARPA) and all the engineers and technicians at Northrop(MIM) capacitors and 100 Q/sq NiCr thin film resistors Grumman who contributed to this work.(TFRs) with reliable operation at 0.6 mA/mm. The MMICdesign is coplanar. As a result, no backside process isrequired after completing front-side processes. Fig. 10 shows Referencesthe rf performance of an X-band LNA using 0.1 gm RfrneInh 2Ae0r8Sb-InAs HEMTs biased at VS = 03 V anding = 6.7 (1) J. B. Boos, W. Kruppa, B. R. Bennett, D. Park, S. W. Kirchoefer, R.Ino2Ao,8SbInA HEMTs biased at Vs = 0.3V a7 D Bass, and H. B. Dietrich, "AlSb/InAs HEMTs for Low-Voltage, High-mA (power 22 mW). The associated gain (Ga) and noise- Speed Applications," Vol.45, pp.1869-1875,1998.figure (NF) at 12 GHz are approximately 12 and 3 dB, (2) W. R. Deal, R. Tsai, M. D. Lange, J. B. Boos, B. R. Bennett, and A.respectively. The rf yield on a 3-inch GaAs substrate is Gutierrez, "A Low Power/Low Noise MMIC Amplifiers for Phased-approximately 80%. For the first time, superior rf Array Applications Using InAs/AlSb HEMT," the Technical Digest ofperformance of LNAs using Ino.2Al08Sb-InAs HEMTs is IEEE IMS Symposium, pp. 2051-2054, 2006.demonstrated. This is essential for phased-array applications (3) B. Y. Ma, J. B. Hacker, J. Bergman, P. Chen, G. Sullivan, G. Nagy, andB. Brar, "Ultra-Low-Power Wideband High Gain InAs/AlSb HEMTwith ultralow-power and oxidation-free requirements. Low Noise Amplifiers," the Technical Digest of IEEE IMS

Symposium, pp. 73-76,2006.(4) W. R. Deal, R. Tsai, M. D. Lange, J. B. Boos, B. R. Bennett, and A.

Gutierrez, "A W-band InAs/AlSb Low-Noise/Low-Power Amplifier,"Conclusion IEEE Microwave and Wireless Components Lett., Vol. 15, pp. 208-

210, 2005.A 0.1 tm Ino 2Alo 8Sb-InAs HEMT MMIC technology was (5) W. R. Deal. R. Tsai, M. Lange, J. B. Boos, B. R. Bennett, R.developed for phased-array applications with ultralow-power Grundbacher, L. J. Lee, K. Padmanabhan, P. H. Liu, C. Namba, P.and oxidation-free requirements. An Ino A10 Sb layer was Nam, and A. Gutierrez, "A 110 GHz AlSb/InAs MMIC Amplifier," the2li a l Technical Digest of GaAs IC Symposium, pp. 301-304, 2004.utilizedto1 replace the upper A*Sb layer in a conventional (6) B. R. Bennett, R. Magno, J. B. Boos, W. Kruppa, and M. G. Ancona,AlSb-InAs HEMT in order to mitigate the oxidation that can "Antimonide-based Compound Semiconductors for Electronic Devices:be incurred by the AlSb layers. In this work, we have A Review," Solid-State Electronics, Vol. 49, pp. 1875-1895, 2005.demonstrated superior dc and rf performance on both devices (7) B. P. Tinkham, B. R. Bennett, R. Magno, B. V. Shanabrook, and J. B.and LNAs using 0.1 tm In Al Sb-InAs HEMTs on 3-inch Boos, "Growth of InAsSb-Channel High Eectron Mobility Transistors02 08 Structures", J. Vac. Sci. Technol. Vol. B23, pp. 1441-1444, 2005.GaAs substrates. For the first time, LNAs of 0.1 m (8) B. R. Bennett, J. B. Boos, M. G. Ancona, N. A. Papanicolaou, G. A.In02Al08Sb-InAs HEMTs are demonstrated - with excellent rf Cooke, and H. Kheyrandish, "InAlSb/InAs/AlGaSb Quantum Wellperformance while operating at ultralow power (2 mW). This Heterostructure for High-Electron-Mobility Transistors", Journal ofaccomplishment is important for phased-array applications Electronic Materials. Vol. 36, pp. 99-104, 2007.with ultralow-power and oxidation-free requirements. (9) N. A. Papanicolaou, B. R. Bennett, J. B. Boos, D. Park and R. Bass,

"Sb-based HEMTS with InAlSb/InAs Heterojunction", ElectronicsLetters. Vol. 41, No. 19, 2005, pp. 1088-1089.

(10)s. Datta, T. Ashley, J. Brask, L. Buckle, M. Doczy, M. Emeny, D.Hayes, K. Hilton, R. Jefferies, T. Martin, T. J. Philips, D. Walls, P.Wilding, and R. Chau, "85 nm Gate Length Enhancement and

16 Depletion mode INSb Quantum Well Transistors for Ultra High SpeedGa P = 2mW and Very Low Power Digital Logic Applications," the Technical Digest

14 _ 8 *o D of International Electron Device Meeting, 2005, pp. 763-766.v2

(11)Y. C. Chou, J. M. Yang, C. H. Lin, J. Lee, M. Lange, R. Tsai, P. Nam,m 12 _ M. Nishimoto, A. Gutierrez, H. Quach, R. Lai, D. Farkas, M.

10 Wojtowicz, P. Chin, M. Barsky, and A. Oki, J. B. Boos, and B. R.U. Bennett, "Manufacturable and Reliable 0.1 ,um AlSb/InAs HEMT2 MMIC Technology for Ultra-Low Power Applications", the Technical-a 8 Digest of IEEE IMS Symposium, 2007.Cu

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Frequency (GHz)

Fig. 10: RF performance of Ga and NF from a 0.1 ,um 1n02Al085b-InAsHEMT X-band low noise amplifier on a 3-inch GaAs substrate.

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