Spintronic device structures
Jaroslav Fabian
Institute for Theoretical PhysicsUniversity of Regensburg
Spintech V Krakow 7.7.2009
Giant Magnetoresistance (GMR) magnetoelectronics
"for the discovery of giant magnetoresistance"Grunberg; Fert (1988)
F F
Julliere
1975; Moodera
et al. 1995
Tunneling Magnetoresistance (TMR)
applications: HDD, MRAM
I
:outline: what can we do with (ensemble) spin in semiconductors
•
road map issues: injection, detection, relaxation•
spin transistors
•
bipolar spintronic
devices•
magnetic resonant tunneling diodes
•
closing
I. Zutic, J. Fabian, and S. Das
Sarma, Spintronics: Fundamentals and applications, Rev. Mod. Phys. 76, 323 (2004)
J. Fabian, A. Matos-Abiague, C. Ertler, P. Stano, and I. Zutic,Semiconductor spintronics, Acta
Physica
Slovaca, 57, 565-907 (2007)
spintronics drive
technology fundamental discoveries
SPINTRONICS GOALSspin control of electrical properties
(I-V characteristics)
electrical control of spin(magnetization)
:semiconductor spintronics devices: spin something
•
spin Zener
diodes•
spin resonant diodes
•
spin field-effect transistors•
magnetic semiconductor tunnel junction devices
•
magnetic unipolar and bipolar junction diodes and transistors•
spin optoelectronic devices
•
spin galvanics devices•
spin Hall polarizers
•
spin-polarized semiconductor lasers•
spin pumping batteries
•
spin-torque devices•
spin ratchets
•
spin memrams•
spin quantum computers
•
...
International Technology Roadmap for Semiconductors:
Emerging Research Logic Devices
risk
RSFQ1-D
structuresresonanttunneling SET molecular QCA
spin transistor
2004
2005, 2006
International Technology Roadmap for Semiconductors:
Emerging Research Logic Devices
risk
RSFQ1-D
structuresresonanttunneling SET molecular QCA
spin transistor
2004
2007, 2008
Intl. Technol. Roadmap for Semiconductor will we have a useful spin transistor?
SPINTRONICS’
3 REQUIREMENTS
•
EFFICIENT SPIN INJECTION
•
(slow) SPIN RELAXATION @ (efficient) SPIN CONTROL
•
RELIABLE SPIN DETECTION
Silsbee-Johnson spin-charge coupling
F N
spin accumulation
S. A. Crooker et al., JAP, 101,081716 (2007)
S. A. Crooker at al., Science 309, 2191 (2005)
:spin injection: made visible
:spin injection: all-semiconductor all-electrical spin injection/detection
cbvbAu/Ti
(Ga,Mn)As
n+-GaAsn+n-GaAs
n-GaAs
x/[010]
-y/[100]
z
Iinj V V V
2 3 4 5 61
L
non-local spin injection/detection device magnetic Esaki diode contacts
Spininjection
M. Ciorga et al., PRB
79,165321 (2009); see poster 161
Pinj 50%
Silsbee-Johnson spin-charge coupling
Q: Suppose there is a source of nonequilibrium spin accumulation
at the far right of N. What is the emf due to the proximity with the equilibrium spin polarization Pj
in F?
spin accumulation
R. H. Silsbee, Bull. Magn. Reson.2, 284 (1980); M. Johnson and R. H. Silsbee, Phys. Rev.
Lett. 55, 1790 (1985)
J. Fabian and I. Zutic, The standard model of spin injection, in book From GMR to Quantum Information, (Forschungszentrums Juelich, 2009), Eds. S. Blügel
et al; also in arXiv:0903.2500
:spin relaxation: GaAs, Si
J. L. Chang, M. W. Wu, and J. Fabian, arXiv:0906.4054
Si
(non-degenerate densities)GaAs
(low temperature)
see also poster 264 (Jiang
and Wu)
:spin relaxation: persistent spin helix: engineering spin lifetime
increased spin injection efficiencyJ. L. Cheng, M. W. Wu,, and I. C. da
Cunha
Lima, Phys. Phys. B 75, 205328 (2007)
individual spin components: short spin lifetime
spin helix: 100-times longer spin lifetime
From J. Fabian, Nature (N&V) 458, 580 (2009)
Theory: B. A. Bernevig, J. O. Orenstein, and S. C. Zhang, Phys. Rev. Lett. 97, 236601 (2006).
Experiment:J. D. Koralek, C. P. Weber, J O. Orenstein,
B. A. Bernevig, S. Z. Zhang, S. Mack, D. D. Awschalom, Nature, 458, 610 (2009).
:materials issues:room temperature ferromagnetic semiconductors?
• 1-15 % Mn• p-doped (Mn
replaces Ga)
• degenerate: p = 1020
- 1021/cm3• Tc
up to 180 K
• fm and p-density coupled• impurity band or not?
T. Jungwirth et al., Rev. Mod. Phys. 78, 809 (2006)
(Ga,Mn)As Fe Au
• above room-temperature fm• a few nm of GaMnAs
involved
• bias control?• anisotropies?
GaMnAs Fe/GaMnAs
F. Maccherozzi et al., Phys. Rev. Lett. 101, 267201 (2008)See also poster 234 for related work S. Mark et al.
intl. Semiconductor roadmap 2007 emerging research logic devices
J. Fabian, A. Matos-Abiague, C. Ertler, P. Stano, and I. Zutic, Semiconductor spintronics, Acta
Phys. Slov, 57, 566 (2007)
:spin transistors:
Datta-Das
Sugahara-Tanaka
Johnson
Magnetic bipolar transistor
hot-electron spin transistors
PresenterPresentation NotesSugahara-tanaka
Bipolar spintronic devices with I. Zutic and S. Das Sarma
•
Spin-polarized pn
junction diode, spin capacitanceI. Zutic, J. Fabian and S. Das
Sarma, Phys. Rev. B 64, 121201 (2001)
•
Spin-polarized solar cellI. Zutic, J. Fabian and S. Das
Sarma, Appl. Phys. Lett. 79, 1558 (2001)
•
Magnetic bipolar diode (MBD), GMR, spinvoltaic
effect, spin injection, spin extractionI. Zutic, J. Fabian and S. Das
Sarma, Phys. Rev. Lett. 88, 066603 (2002)
•
General theory of magnetic bipolar devicesJ. Fabian. I. Zutic, and S. Das
Sarma, Phys. Rev. B 66, 165301 (2002)•
Magnetic bipolar transistor (MBT), magnetoamplificationJ. Fabian, I. Zutic, and S. Das
Sarma, cond-mat/0211639; Appl. Phys. Lett. 84, 85 (2004)J. Fabian and I. Zutic, Phys. Rev. B 69, 115314 (2004); Appl. Phys. Lett. (2005)
•
Spin injection into silicon: bipolar modeI. Zutic, J. Fabian, and S. Erwin, Phys. Rev. Lett. 97, 026602 (2006)
“he is bipolar”
Bipolar spintronic devices with I. Zutic and S. Das Sarma
•
Spin-polarized pn
junction diode, spin capacitanceI. Zutic, J. Fabian and S. Das
Sarma, Phys. Rev. B 64, 121201 (2001)
•
Spin-polarized solar cellI. Zutic, J. Fabian and S. Das
Sarma, Appl. Phys. Lett. 79, 1558 (2001)
•
Magnetic bipolar diode (MBD), GMR, spinvoltaic
effect, spin injection, spin extractionI. Zutic, J. Fabian and S. Das
Sarma, Phys. Rev. Lett. 88, 066603 (2002)
•
General theory of magnetic bipolar devicesJ. Fabian. I. Zutic, and S. Das
Sarma, Phys. Rev. B 66, 165301 (2002)•
Magnetic bipolar transistor (MBT), magnetoamplificationJ. Fabian, I. Zutic, and S. Das
Sarma, cond-mat/0211639; Appl. Phys. Lett. 84, 85 (2004)J. Fabian and I. Zutic, Phys. Rev. B 69, 115314 (2004); Appl. Phys. Lett. (2005)
•
Spin injection into silicon: bipolar modeI. Zutic, J. Fabian, and S. Erwin, Phys. Rev. Lett. 97, 026602 (2006)
“he is bipolar”
CONVENTIONAL DIODE 101
ratchet and paw analog of a pn
junction diode
pn
generation current recombination current
:magnetic diode: spin-voltaic effect: spin-charge coupling
GiantMagnetoResistance
in MDs
Spin-charge coupling: proximity of equilibrium (Pp
) and nonequilibrium
(δPn
)spin
what is in the numerics?
drift-diffusion
n-emitter p-m-base
n-collector
think of Stern-Gerlach
charge and spin continuity
spin relaxation
self-consistency with electrostatics
:analytical modeling: generalized Shockley theory
carrier and spin quasiequilibrium in space-charge regions
(constant spin-resolved chemical potentials)
+
continuity of spin current through space-charge regions
J. Fabian, I. Zutic, S. Das Sarma, Phys. Rev. B 66, 165301 (2002)
:magnetic pn
junctions: qualitative statements
•
Impossibility of spin injection at low biases•
Spin injection of nonequilibrium
spin only (beyond the
standard spin injection model)•
Spin-charge coupling
J. Fabian, A. Matos-Abiague, C. Ertler, and P. Stano, Semiconductor spintronics, Acta
Phys. Slov, 57, 566 (2007)
Magnetic pn
junction arrays (matrix theory):
experimental observation of spin-voltaic effect in a paramagnetic
pn junction
T. Kondo, J. Hayafuji, and H. Munekata,Investigation of spin-voltaic effect in a p-n
heterojunctions,Jpn. J. Appl. Phys. 45, L663 (2006)
experimental observation of spin-voltaic effect in a ferromagnetic pn junctionP. Chen, J. Moser, P. Kotissek, J. Sadowski, M. Zenger, D. Weiss, and W. WegscheiderAll electrical measurement of spin injection in a magnetic p-n
junction diode,Phys. Rev. B 74, 24302 (R) (2006)
:spin-injection Hall effect:spin-polarized pn junction & local extraordinary Hall transport
J. Wunderlich
et al, Nature Phys. (in press); arXiv:0811.3486 (see poster 288)
• Local (50-100 nm) nondistructive
electric measurement of spin polarization
• high-temperature (200 K) operation• probe of fundamental spin-orbit (spin helix) physics
bipolar junction transistor
•
ultra high speed digital circuits•
small-signal amplification
•
high frequency analog circuits (SiGe, GaAs
HBTs)•
integrated Circuits market: 20% BJT, 75% MOSFET
microphone
base
emitter
collector
ee
e
:magnetic bipolar transistor (MBT):J. Fabian, I. Zutic and S. Das Sarma, cond-mat/0211639 (2002); Appl. Phys. Lett. 84, 85 (2004);J. Fabian and I. Zutic, Phys. Rev. B 69, 115314 (2004).
• all semiconductor• magnetic semiconductor active region• versatile design• materials restricted
M. Flatte, Z. G. Yu, E. Johnston-Halperin, and D. D. Awschalom, Appl. Phys. Lett. 82, 4740 (2003)N. Lebedeva
and P. Kuivalainen, J. Appl. Phys. 93, 9845 (2003)
:spin-polarized bipolar lasers: reducing the threshold power
J. Rudolph et al., APL 87, 241117 (2005); 82, 4516 (2003)
M. Holub
et al., PRL 98, 146603 (2007)
optical injection of spin-polarized carriers provides a threshold current reduction for the lasing operation
• Limited theoretical understanding
• Threshold strongly depends on the recombination mechanism
• Maximum threshold
reduction larger than previously thought possible
• Very short spin relaxation time of holes is advantageous
electrical spin injection threshold reduction
I. Vurgaftman
et al., APL 93, 031102 (2008)
C. Gothgen, R. Oszwaldowski, A. Petrou, I. Zutic, APL 93, 042513 (2008)
Magnetic
Resonant
Tunnel
Diodes A. Slobodskyy
et al, Phys. Rev. Lett. 90, 246601 (2003)
C. Ertler
and J. Fabian, Appl. Phys. Lett. 89, 193507 (2006)
C. Ertler
and J. Fabian, Phys. Rev. B 75 195323 (2007)
• efficient spin filtering• spin detection• fast switching times• coherence issues• RT operation?
6T
3T
0T
8% Mn
T=1.3K
a)
b)
BeZnSe
ZnMnSeZnSe
ZnSe
BeZnSeBeZnSe
ZnMnSeZnSe
ZnSe
BeZnSe
ZnSeZnMnSe
ZnSe
B
1.3
K
Voltage (0-0.2 V)
Cur
rent
(0-1
50 μ
A)
0 0.05 0.1 0.15 0.2 0.250
0.5
1
1.5
2
2.5
3x 10
5
Voltage (V)
Cur
rent
Den
sity
(A
/cm
2 )
0 10 20 300
50
100
z (nm)
Ene
rgy
(meV
)
Δ E = 0Δ E = 5 meVΔ E = 10 meVΔ E = 15 meVΔ E = 20 meVΔ E = 25 meVΔ E = 40 meV
T = 4.2 K
ΔV2out
ΔV3out
ΔV1out
see posters 168 –
174, 176, 177, 181, 219, 242, 284
:Digital Magneto
Resistance (DMR): Ertler and Fabian, Appl. Phys. Lett. 89, 193507 (2006)
mono-to-bistable logic element (mobile) (multi-valued logic roadmap, up to 100 GHz demo)
Maezawa and Mizutani, Jpn. J. Appl. Phys. 32, L42 (1993)
Driver mRTD
Load RTD
Vin
B
Vout
I
Vout
Vin Vinmono
mono
low
high
Vload
= Vin
– Vout
, Iload
=Idriver
load driver
operational principle of DMR
Vout
Vin
mRTD
RTD
B
Vin
B
Vout
threshold
mono mono
lowhigh high
mono mono
C. Ertler
and J. Fabian, Appl. Phys. Lett. 89, 193507 (2006); Phys. Rev. B 75, 195323 (2007)
:self-sustained magneto-electric oscillations in MRTDs: C. Ertler
and J. Fabian, Phys. Rev. Lett. 101, 077 202 (2008) ; poster 168
see also poster 169, Carretero
et al. for related work
0 10 20 300
5
10
x 1015
Voltage (mV)
j (a.
u.)
jmaxjmin
I
II
(a)
0 10 20 300
5
10
15
20
Voltage (mV)
Δ (m
eV)
Δmax
Δmin
(b)
II
I
50 100 150 2000
5
10
x 1015
Time (t*)
j (a.
u.)
jtot
j↑j↓
(c)
50 100 150 2002
4
6
8
10
12
14x 1011
Time (t*)
n (1
/cm
2 )
ntotn↑n↓
(d)
Non-linear coupling of charge, magnetization, and current leads to temporal oscillations of the current etc under dc bias
Intl. Technol. Roadmap for Semiconductor will we have a useful spin transistor?
Intl. Technol. Roadmap for Semiconductor will we have a useful spin transistor?
too ea
rly to
say
:conclusions:
•
demonstrate spintronic
device schemes •
new fm materials/materials combinations
•
new physical principles for spin-based devices•
involve electrical engineers
SFB 689
SPP 1285
DFG Collaborative Research Center (Regensburg)“Spin phenomena in reduced dimensions”
DFG Priority Program “Semiconductor Spintronics”
Spintronic device structures�Giant Magnetoresistance (GMR)�magnetoelectronics:outline:�what can we do with (ensemble) spin in semiconductorsspintronics drive�SPINTRONICS GOALS:semiconductor spintronics devices:�spin somethingInternational Technology Roadmap for Semiconductors:�Emerging Research Logic DevicesInternational Technology Roadmap for Semiconductors:�Emerging Research Logic DevicesIntl. Technol. Roadmap for Semiconductor�will we have a useful spin transistor?SPINTRONICS’ 3 REQUIREMENTS�Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16intl. Semiconductor roadmap 2007�emerging research logic devicesSlide Number 18Slide Number 19Bipolar spintronic devices� with I. Zutic and S. Das SarmaBipolar spintronic devices� with I. Zutic and S. Das SarmaSlide Number 22ratchet and paw analog of a pn junction diode:magnetic diode:�spin-voltaic effect: spin-charge couplingGiantMagnetoResistance in MDswhat is in the numerics?drift-diffusioncharge and spin continuityself-consistency with �electrostatics:analytical modeling:�generalized Shockley theorySlide Number 31experimental observation of �spin-voltaic effect in a paramagnetic pn junctionexperimental observation of �spin-voltaic effect in a ferromagnetic pn junctionSlide Number 34bipolar junction transistor:magnetic bipolar transistor (MBT)::spin-polarized bipolar lasers:�reducing the threshold power�Magnetic Resonant Tunnel Diodes�A. Slobodskyy et al, Phys. Rev. Lett. 90, 246601 (2003)�C. Ertler and J. Fabian, Appl. Phys. Lett. 89, 193507 (2006)�C. Ertler and J. Fabian, Phys. Rev. B 75 195323 (2007) �:Digital Magneto Resistance (DMR):�Ertler and Fabian, Appl. Phys. Lett. 89, 193507 (2006) �mono-to-bistable logic element (mobile) �(multi-valued logic roadmap, up to 100 GHz demo)�Maezawa and Mizutani, Jpn. J. Appl. Phys. 32, L42 (1993)�operational principle of DMR:self-sustained magneto-electric oscillations in MRTDs:�C. Ertler and J. Fabian, Phys. Rev. Lett. 101, 077 202 (2008) ; poster 168�see also poster 169, Carretero et al. for related work Intl. Technol. Roadmap for Semiconductor�will we have a useful spin transistor?Intl. Technol. Roadmap for Semiconductor�will we have a useful spin transistor?:conclusions: