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The state-of-the-art InP-based HEMTs Ankit Sharma ECE695 20 Feb, 2015

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Brief History Proposed by Takashi Mimura (Fujitsu Ltd) in 1979. N-type AlGaAs layer thickness varied

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Why InP based HEMTs ? GaAs-based HEMT InP-based HEMT e - in InP-based HEMT: lower effective mass, hence higher mobility High saturation velocity High electron concentration InP-based HEMTs Higher Speed !

Slide 4 2.7 mS/um." ieee international electron devices meeting, washington dc, december 5-7, 2011."> 2.7 mS/um.">

III-V HEMT : record f T vs time fT=688 GHz and fmax=800 GHz in Lg=40 nm In0.7Ga0.3As MHEMTs with gm,max>2.7 mS/um." IEEE International Electron Devices Meeting, Washington DC, December 5-7, 2011.

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2004 : Shinohara Keisuke and Matsui Toshiaki Gate length < 50 nm T-shaped gate electrode (using Electron Beam Lithography) Enables reduction of gate length while maintaining a large cross- sectional area to minimize the gate resistance. TEM cross-section of T-shaped gate |h 21 | 2 (dB) Freq (GHz) SHINOHARA, Keisuke, and Toshiaki MATSUI. "3-7 Nano-Gate TransstorWorld's Fastest InP-HEMT." Journal of the National Institute of Information and Communications Technology 51 (2004): 95-102.

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2007 : Northrop Grumman Space Tech., CA Gate length < 50 nm Proposed a number of process enhancements Reduction of ohmic contact resistance through a higher doped cap layer design coupled with InAs/InGaAs channel grown by MBE. Sheet resistance of epitaxial layers is lowered to 75 ohm/sq. (compared to 110 ohm/sq. earlier) Mobility improved to 15000 cm 2 /V.sec (compared to 12000 cm 2 /V.sec) Fig 3. Calculated Fmax Lai, R. ; Northrop Grumman Space Technol., Redondo Beach, Electron Devices Meeting, pp. 609- 611, 2007. IEDM 2007. IEEE International

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2007 : Y. Nakasha et.al (Fujitsu) T-shaped gate suffers with poor physical strength at the junction between a large top and narrow stem. Proposed Y-shaped gate structure. Results in high yield. Use BCB (Benzocyclobutene) as inter-layer dielectric to achieve low dielectric constant (2.8) along with cavity around gate for enhancing speed. Results in a speed gain of about 14% Kawano, V. Yasuhiro Nakasha V. Yoichi, V. Masaru Sato, and V. Tsuyoshi Takahashi V. Kiyoshi Hamaguchi. "Ultra high-speed and ultra low-noise InP HEMTs." Fujitsu Sci. Tech. J 43.4 (2007): 486-494.

Slide 8 2.7 mS/um." ieee international electron devices meeting, washington dc, december 5-7, 2011."> 2.7 mS/um.">

F T = 688 GHz ; F MAX = 800 GHz 2011 : Jess A. del Alamo (MIT) fT=688 GHz and fmax=800 GHz in Lg=40 nm In0.7Ga0.3As MHEMTs with gm,max>2.7 mS/um." IEEE International Electron Devices Meeting, Washington DC, December 5-7, 2011.

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F T = 850 GHz ; F MAX = 1.42 THz 25 nm gate-stem, 30 nm gate length Also enable frontside and backside feature scaling to increase speed. 2014 : Northrop Grumman Space Tech., CA Deal, WR. ; Northrop Grumman Space Technol., Redondo Beach, Infrared, Millimeter, and Terahertz waves (IRMMW-THz), 2014 39th International Conference, pp 1-3, Sept 2014

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Conclusion