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Real Space Transfer...

Real Space Transfer. ...Karl’s Baby Matures !. July 1976. page 55. Real-Space Transfer. return back may be slow at least at low temperatures. RST versus MST. microwave activity in RST is hard to experimentally distinguish from that arising from the Gunn (MST) effect.

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Real Space Transfer...

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  1. Real Space Transfer... ...Karl’s Baby Matures ! Karl Hess Symposium, May 2006

  2. July 1976

  3. page 55

  4. Real-Space Transfer return back may be slow at least at low temperatures

  5. RST versus MST microwave activity in RST is hard to experimentally distinguish from that arising from the Gunn (MST) effect The interplay between the RST and the Gunn effect treated magisterially by Kizilyalli and Hess (1989) by Monte-Carlo simulation of hot electrons in GaAs/AlGaAs heterostructures Karl Hess Symposium, May 2006

  6. Anode Collector S D B Ch Substrate Cathode Heater Real Space Transfer Transistors Controlling the effective electron temperatureTe Current Thigh Tlow Voltage RST Transistor: CHINT Kastalsky and Luryi (1983) Karl Hess Symposium, May 2006

  7. Compound semiconductor CHINT Bell Labs, 1990-93 Karl Hess Symposium, May 2006

  8. I-V Characteristics Mensz et al (APL 1990) gm > 10 S/mm PTV > 100 at 4 K ....... PTV > 10,000 at 300 K ....... PTV > ∞ quest over Karl Hess Symposium, May 2006

  9. 1 k o 0 s a t b Drain Current (A/cm) -1 c u 0.15 d d a c b -2 0.10 VC= 2V Electron temperature, eV -3 0.05 d -4 0.00 Electron Temperature (eV) -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 0 1 2 3 4 5 Source-Drain Voltage (V) Source-Drain Distance (μm) Broken symmetry states Luryi and Pinto (Phys. Rev. Lett. 1991) Karl Hess Symposium, May 2006

  10. Collector S D B Ch Substrate Frequency Characteristicsup your collectors, gentlemen ! Maezawa and Mizutani (1991) analyzed CHINT versus FET mode in the same device: CHINT three times faster! But heed Karl’s warning about MST interference, Gunn is relatively slow ! Belenky et al (1993) Karl Hess Symposium, May 2006

  11. Materials GaAs/AlGas Kastalsky, Luryi, Gossard (1983-84) InGaAs/InAlAs Luryi, Mensz, Cho (1989-91) LED CHINT Mastrapasqua (1993) InGaAs/InP Belenky, Luryi, Cho, Hamm (1993) Si/GeSi Mastrapasqua, King (1996) Bi/Si triode Luryi, Tung (1988) unsuccessful Si/high κ believe feasible, ideal for SOI Si/high-K believe can be done, ideally SOI Maturity is when silicon does it ! Karl Hess Symposium, May 2006

  12. Desired Si/high-K structures undoped Si channel low-barrier dielectric collector SiO2 pSi substrate n+ polySi Bulk Si substrate SOI Karl Hess Symposium, May 2006

  13. Si Zr {x} Si {1-x} O2 What’s no good for the goose… … may be sauce for the gander ! Kawamoto et al, J. Appl. Phys. 90, 1333-1341 (2001) silicon – zirconium silicate Karl Hess Symposium, May 2006

  14. What controls band offsets ? Charge transfer between “virtual gap states” (VGS) – a.k.a. “metal-induced gap states” (MIGS) – to establish a common Fermi level, called the charge neutrality level (CNL) CB CB CB offset SBH CNL CNL VB offset VB VB Si Oxide Metal Oxide CNL of Si is low in the gap (0.2 eV); for most oxides it is high in the gap…hence low CB offset Karl Hess Symposium, May 2006

  15. Calculated band offsets (between Si and metal oxides) one man’s worry is another man’s joy ! J. Robertson,MRS Bulletin (March 2002)http://www.mrs.org/publications/bulletin Karl Hess Symposium, May 2006

  16. (1) higher µ (2) lower FG advantages: undoped Si channel low-barrier dielectric collector SiO2 pSi substrate n+ polySi Why SOI ? Bulk Si substrate SOI Karl Hess Symposium, May 2006

  17. Speed of silicon CHINT • In principle, Si CHINT is faster than GaAs, etc • In compound semiconductors the RST is slowed by the momentum-space transfer (Karl Hess) recall: InGaAs/InP was faster than InGaAs/InAlAs • SOI minimizes parasitic capacitances • drain to body especially (D – control electrode!) • Expect subpicosecond operation • Hey, silly cone, where are you ? We wanna mature ! Karl Hess Symposium, May 2006

  18. Symmetry and Logic S D IC = XOR (S, D) C similar symmetry exists in FET: but it is not important, because G is not the output terminal Karl Hess Symposium, May 2006

  19. ORNAND cyclical electrode symmetry: X3 X1 X2 X3 OR barrier C NAND IC = ORNAND (X1, X2, X3) Karl Hess Symposium, May 2006

  20. Expt: CHINT LED • Mastrapasqua et al, 1993 • InGaAs/InAlAs • Complementary collector • ORNAND function – both electric and optical • T = 300 K • Later Si/GeSi ORNAND (electrical only, of course) Karl Hess Symposium, May 2006

  21. Preliminary verdict Real space transfer Si/high-K transistors • Highly desirable, functional high-speed device, perfectly compatible with VLSI, ideal for SOI • Unproven, hopefully will come out as a bonus of the currently fashionable quest for high-K gate dielectrics • NDR controlled by 3rd terminal – immediate applications as VCO • Higher-level logic... value questionable • Worth pursuing Karl Hess Symposium, May 2006

  22. When Karl’s baby matures... ... silicon takes over the RST ... I shall also retire in Hawaii ... and we shall scream: III-V’s were first ! but will silicon listen ? “Here lies Gallium R. Senide, brash and romantic youth” Karl Hess Symposium, May 2006

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