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The magnetically sensitive transistor (also known as the spin transistor or spintronic transistor—named for spintronics, the technology which this development spawned), originally proposed in 1990 and …

The magnetically sensitive transistor (also known as the spin transistor or spintronic transistor—named for spintronics, the technology which this development spawned), originally proposed in 1990 and currently still being developed, is an improved design on the common transistor invented in the 1940s. The spin transistor comes about as a result of research on the ability of electrons (and other fermions) to naturally exhibit one of two (and only two) states of spin: known as "spin up" and "spin down". Unlike its namesake predecessor, which operates on an electric current, spin transistors operate on electrons on a more fundamental level; it is essentially the application of electrons set in particular states of spin to store information.

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  • 1. SpinFET Raja Shekar Baddula – 134366001 Sreejith K P – 133076005 Titto Thomas – 133079015 Nandakumar S R - 133070053
  • 2. Need of Nanostructure device     Miniaturization Problems Power dissipation Short channel effects Quantum mechanical effects  ballistic  tunneling Spin FET  Spin of a electron S = ħσ/2  Magnetic moment of a electron µspin = -gµBS/ ħ σ = Pauli spin operator µB = Bohr magnetron (eħ/2m) http://www.nims.go.jp/apfim/SpinFET.html EE733 : SpinFET 2
  • 3. Spin-Orbit interaction Heterojunction: Atomic case Enucleus ˆ Ze r  4 0 r 2 AlGaAs j  Zev InGaAs  In analogy with the atomic case Rashba S-O term  In Electron rest frame Amperes' law B 0 j  r 4 r 2 E Beff  0 0 (v  Enucleus ) S O    spin Beff  H S O g B S (v  E ) 2 hc g  B  ( p  V ) 2 2mc   ,k  x   ,k  k y k   ,k  y   ,k    ,k  z   ,k  0 EE733 : SpinFET kx k dV ˆ V  z g B dz dV H S O  [ ( p  z )] 2 2mc dz g B dV H S O  [z (  p)] 2 2mc dz  H S O  [ z (  p)] h 1  2 2 H ( px  p y )  ( x p y   y px ) 2m h 3
  • 4. Giant magnetoresistance (GMR) RA: Resistance in the antiparallel configuration RP: Resistance in the parallel configuration http://www.aist.go.jp/aist_e/latest_research/2004/20041124/20041124.html http://www.nims.go.jp/apfim/halfmetal.html http://www.directvacuum.com/spin.asp EE733 : SpinFET 4
  • 5. Origin of GMR  Mott Model  Different resistivities  Scattering is : Parallel Antiparallel  Strong for electrons with spin antiparallel to the magnetization direction  Weak for electrons with spin parallel to the magnetization direction H. Ehrenreich and F. Spaepen, Academic Press, 2001, Vol. 56 pp.113-237 http://physics.unl.edu/tsymbal/reference/giant_magnetoresistance/origin_of_gmr.shtml EE733 : SpinFET 5
  • 6. SpinFET : Structure & Working EE733 : SpinFET 6
  • 7. Electron spin photon polarization Supriyo Datta & Biswajit Das, Electronic analog of the eiectro-optic modulator, APL ,1989 http://nanohub.org/resources/11128 EE733 : SpinFET 7
  • 8. Structure & Working of spinFET = Supriyo Datta & Biswajit Das, Electronic analog of the eiectro-optic modulator, APL ,1989 Satoshi Sugahara and Junsaku Nitta, Spin-Transistor Electronics: An Overview and Outlook, 2010 http://nanohub.org/resources/11128 EE733 : SpinFET 8
  • 9. Spin Injection  Source(polarizer) and drain(analyzer) ferromagnetic material(Fe). made of  Conditions with the polarizer (source) and analyzer (drain) magnetizations parallel or antiparallel, resulting in relatively high or low spin-dependent voltages at the detector.  Conductance(G) = 𝑞2 𝐷/𝑡. Supriyo Datta & Biswajit Das, Electronic analog of the eiectro-optic modulator, APL ,1989 Satoshi Sugahara and Junsaku Nitta, Spin-Transistor Electronics: An Overview and Outlook, 2010 http://nanohub.org/resources/11128 EE733 : SpinFET 9
  • 10. Channel Requirements  2DEGs in narrow band gap semiconductor  Ballistic tranport  Avoid spin relaxation[1]  Elliot Yafet [2]  D'yakonov-Perl  Bir-Aronov-Pikus [1] J. Fabian and S. Das Sarma, Spin relaxation of conduction electrons, 1993 [2] Satoshi Sugahara and Junsaku Nitta, Spin-Transistor Electronics: An Overview and Outlook, 2010 EE733 : SpinFET 10
  • 11. Electrostatic control of spin  Aharonov – Bohm Experiment [1] Conductance [2] variation Phase difference in the  Applied potential controls the polarization of the electron wave vector 𝟐 𝒎∗ 𝜼𝒍 ∆𝜽 = ћ𝟐 [1] J. Nitta, F. E. Meijer, and H. Takayanagi, Spin-interference device, 1999 [2] Satoshi Sugahara and Junsaku Nitta, Spin-Transistor Electronics: An Overview and Outlook, 2010 EE733 : SpinFET 11
  • 12. Gate control of the channel Satoshi Sugahara and Junsaku Nitta, Spin-Transistor Electronics: An Overview and Outlook, 2010 EE733 : SpinFET 12
  • 13. Non-ballistic SpinFET Scattering tolerent Dresselhaus spin-orbit coupling Making both the coefficients equal [1] J. Schliemann, J. C. Egues, and D. Loss, Nonballistic spin-field-effect transistor, 2003 [1] Satoshi Sugahara and Junsaku Nitta, Spin-Transistor Electronics: An Overview and Outlook, 2010 EE733 : SpinFET 13
  • 14. SpinFET improvemts  Improvements [1]  Holes as carriers  Strain engineering to shift the hole subbands  Modified device structure  Gate control hinderance [2]  Fano resonance  Ramsauer resonance  Dual gate as an option [1] D. M. Gvozdie, U. Ekenberg, and I. Thylen, Comparison of performance of spin transistors with conventional transistors, 2005 [2] J. Wan, M. Cahay, and S. Bandyopadhyay, Proposal for a dual-gate spin field effect transistor: A device with very small switching voltage and a large ON to OFF conductance ratio, 2008 EE733 : SpinFET 14
  • 15. Spintronics so far.. EE733 : SpinFET 15
  • 16. Giant Magneto-Resistance (GMR)  Discovered by Albert Fert and Peter Gruenberg independently in 1988.  IBM researcher Stuart Parkin created hard disk read heads, which tremendously improved data storage and speed.  Nobel prize for GMR in 2007. EE733 : SpinFET 16
  • 17. Memory Applications MRAM Non-volatile Lower power consumption than a DRAM Write power only slightly greater than read. Slightly lower performance than SRAM Viewed as a universal memory element. EE733 : SpinFET 17
  • 18. SpinFET based Memory  Depending on the relative direction of magnetization of Free electrode relative to the Fixed magnetization electrode the channel will provide a low/high resistance . EE733 : SpinFET 18
  • 19. Logic Applications AND Logic NAND Logic Magnetoelectric Spin-FET for Memory, Logic,and Amplifier Applications, S. G. Tan et al., 2005 EE733 : SpinFET 19
  • 20. Things that gives hope..  A family of silicon-based semiconductors that exhibit magnetic properties has been discovered in 2004.  A team of Princeton scientists has turned semiconductors into magnets by the precise placement of metal atoms within a material from which chips are made in 2006.  Scientists prove the existence of a spin battery. EE733 : SpinFET 20
  • 21. Thank You EE733 : SpinFET 21