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: