The document discusses Spin Field Effect Transistors (SpinFETs), focusing on their structure, working principles, and applications in memory and logic devices. Key concepts include electron spin, spin injection, and giant magnetoresistance, along with advancements in semiconductor technologies. The importance of controlling spin and polarization through electrostatic means is highlighted, along with potential future developments in spintronics.

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