Handbook of Spintronic Semiconductors

368 Pages·2010·7.81 MB·English

by  Chen W.M., Buyanova I.A. (eds.)

Published by
Pan Stanford Publishing Pte. Ltd.
Penthouse Level, Suntec Tower 3
8 Temasek Boulevard
Singapore 038988
Email: [email protected]
Web: www.panstanford.com
British Library Cataloguing-in-Publication Data
A catalogue record for this book is available from the British Library.
HANDBOOK OF SPINTRONIC SEMICONDUCTORS
Copyright © 2010 by Pan Stanford Publishing Pte. Ltd.
All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or
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ISBN-13978-981-4267-36-6
ISBN-10981-4267-36-8
Printed in Singapore.
Rhaimie - Hdbk of Spintronic Semiconductors.p1md 10/2/2009, 1:28 PM
September8,2009 9:9 RPS:PSPBookIDPSP0012-6.5inx9.75in preface
Preface
With the limits of microelectronic miniaturization in sight there has been an
enormous drive to innovate radically new technologies. As an addition or
alternativetoelectroncharge,the storageandtransportofelectronspinin“spin-
tronics” can not only improve the performance of and add new functionali-
ties to existing devices but also could revolutionize electronics, leading to new
spin-enableddevicessuchasmagneticRAM,spintransistors,spinoptoelectronic
devices,andspinquantumcomputers. Spintronicsopensthedoortoanewgener-
ationofveryhighspeed,verylowpowerdevicesforcomputationanddatatrans-
mission, to the integration of processing and storage capabilities thus far carried
out separately, and to the merging of electronics, photonics and magnetics into
singletechnologiesformultifunctionaldevices.
The success of spintronics relies on the ability to create, control, maintain,
manipulate and detect spin orientation and coherence over practical time and
length scales. An essential element of a spintronic device, and perhapsthe most
challenging, isaspinsourcethroughwhichadesiredspinorientationandcoher-
ence can be generated. Recent demonstration of ferromagnetism in dilute mag-
neticsemiconductors(DMS)andspininjectionfromDMShasshownthepromise
ofDMSasaspinsourcethatiscompatiblewithexistingsemiconductortechnology.
Drivenbythepotentialoffutureapplications, therehavebeenintensive research
effortsworldwide duringrecentyearsinthedevelopmentof spintronicsemicon-
ductors, in understanding their physical properties, and in exploring their spin-
enablingfunctionalityfordeviceapplications. Significantprogresshasbeenmade
boththeoreticallyandexperimentally,whilemanyopenquestionsstillremain.
This book provides an in-depth review of the rapidly developing field of
spintronic semiconductors by a group of leading experts in the field. It covers a
broad range of topics, including growth and basic physical properties of dilute
magnetic semiconductors based on II–VI, III–V and IV semiconductors, recent
developmentsintheoryandexperimentaltechniques,andpotentialdeviceappli-
cations. The aim is to provide postgraduate students, researchers and engineers
a comprehensive overview of our present knowledge and future perspectives of
spintronicsemiconductors.
Wewouldliketothankallofthecontributorsforsharingtheirexperienceand
expertisewithinterestedreadersandforconveying,throughtheirexcellentchap-
ters,theirpassionsforthisexcitingareaofresearch.Wewouldalsoliketoexpress
ourgratitudetoPanStanfordPublishingforoureffectivecollaboration.
WeiminM.ChenandIrinaA.Buyanova
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Contents
Preface v
1. ComputationalMaterialsDesigninSemiconductorNano-spintronics 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1.1 GordonMoore’sLawandBeyondSi-CMOS . . . . . . . . . 2
1.1.2 SemiconductorNano-spintronics . . . . . . . . . . . . . . . 2
1.1.3 Computational Nano-materials Design and the CMD(cid:13)R
System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1.4 AbinitioCalculationofElectronicStructureandMagnetic
MechanismsinDiluteMagneticSemiconductors(DMS) . . 4
1.1.5 Inhomogeneous DMS Caused by Spinodal Nano-
decomposition . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1.6 3D Dairiseki Phase and 1D Konbu Phase as a Quantum
DotandNanoWire . . . . . . . . . . . . . . . . . . . . . . . 5
1.1.7 Colossal Magnetic Response by Electric Field and
PhotonicExcitation . . . . . . . . . . . . . . . . . . . . . . . 7
1.1.8 Spincaloritronics . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.1.9 OrganizationofThisChapter . . . . . . . . . . . . . . . . . 10
1.2 III–VandII–VICompoundSemiconductorBasedDMSbyLDA . . 11
1.2.1 ElectronicStructureandChemicalTrends . . . . . . . . . . 12
1.2.2 FerromagneticMechanismintheDMS . . . . . . . . . . . . 16
1.2.3 CurieTemperature(T )ofHomogeneousSystems . . . . . 20
C
1.3 Spinodal Nano-decomposition in Diluted Magnetic
Semiconductors(DMS) . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.3.1 Inhomogeneous Distributionof Transition Metal
Impurities inDMS . . . . . . . . . . . . . . . . . . . . . . . . 23
1.3.2 MixingFreeEnergyandPhaseStability . . . . . . . . . . . 24
1.3.3 EffectiveChemical-PairInteractionsintheDMS. . . . . . . 26
1.3.4 SimulationoftheSpinodalNano-decomposition . . . . . . 27
1.3.5 Three-dimensional Spinodal Decomposition (Dairiseki
Phase) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1.3.6 Two-dimensionalSpinodalDecomposition(KonbuPhase) 29
1.3.7 Co-dopingMethodforControllingSpinodalDecomposition 31
1.3.8 Super-paramagneticBlockingPhenomena . . . . . . . . . . 33
1.3.9 ApplicationsoftheKonbuPhase . . . . . . . . . . . . . . . 35
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viii Contents
1.3.10 Spin Caloritronics Application in Colossal Spin-Entropy
ExpansionCoolingbytheKonbuPhase . . . . . . . . . . . 38
1.4 ZnOandGaN-basedDMSbySIC-LDA . . . . . . . . . . . . . . . . 41
1.4.1 Pseudo-Self-Interaction-Corrected Local Density
Approximation(SIC-LDA)Method . . . . . . . . . . . . . . 42
1.4.2 ZnO-BasedDMSsinSCI-LDAVersusLDA . . . . . . . . . 44
1.4.3 Mn-DopedGaNinSIC-LDAVersusLDA . . . . . . . . . . 47
1.4.4 CalculatedDensityofStates(DOS)byLDAandSIC-LDA
VersusX-rayPhotoemissionSpectroscopy(XPS) . . . . . . 49
1.5 TiO BasedDMSbyLDAVersusSIC-LDA . . . . . . . . . . . . . . 52
2
1.5.1 ElectronicStructureof(Ti,Co)O . . . . . . . . . . . . . . . 53
2
1.5.2 ElectronicStructureofHostTiO : LDAVersusSIC-LDA . . 56
2
1.5.3 Electronic Structure of (Ti, Co)O and n-type (Ti, Co)O
2 2
with Oxygen Vacancy (Double Donor): LDA Versus SIC-
LDA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
1.5.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
1.6 A New Class of Dilute Magnetic Semiconductors without
TransitionMetalElements . . . . . . . . . . . . . . . . . . . . . . . . 60
1.6.1 Deep Impurity Band Based Dilute Ferromagnetic
Semiconductors without Transition Metal Impurities:
SIC-LDAVersusLDA . . . . . . . . . . . . . . . . . . . . . . 61
1.6.2 SiO -BasedDMS . . . . . . . . . . . . . . . . . . . . . . . . . 63
2
1.6.3 CarbonDopedAlkalineEarthMetalOxides . . . . . . . . . 64
1.6.4 NitrogenDopedAlkalineEarthMetalOxides . . . . . . . . 68
1.6.5 NitrogenDopedMgSandMgSe . . . . . . . . . . . . . . . . 70
1.6.6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
1.7 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2. TransitionMetalDopedZnO 81
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
2.2 DMSTheory: ThePhysicalOriginsofFerromagnetisminDMS . . 83
2.2.1 Dietl’sMean-FieldTheory . . . . . . . . . . . . . . . . . . . 84
2.2.2 First-PrinciplesDesign: DFTCalculations . . . . . . . . . . 85
2.2.3 FerromagnetisminaLocalizedCarrierRegime . . . . . . . 85
2.2.4 FerromagnetisminaSpin-SplitConductionBand . . . . . . 87
2.3 ExperimentalProgressinZnODMS . . . . . . . . . . . . . . . . . . 88
2.3.1 Mn-DopedZnO . . . . . . . . . . . . . . . . . . . . . . . . . 88
2.3.2 Co-DopedZnO. . . . . . . . . . . . . . . . . . . . . . . . . . 94
2.4 ConclusionsandOutlook . . . . . . . . . . . . . . . . . . . . . . . . 99
3. SpintronicsinIII-NitrideBasedMaterials 103
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
3.2 MaterialSelectionforSpintronicSemiconductors. . . . . . . . . . . 104
3.3 ModelsfortheMechanismsofFerromagnetism . . . . . . . . . . . 108
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3.3.1 FreeCarrierMediatedModel . . . . . . . . . . . . . . . . . 108
3.3.2 PercolationModel . . . . . . . . . . . . . . . . . . . . . . . . 109
3.3.3 ExtensiontoRareEarthMagneticImpurities . . . . . . . . 109
3.3.4 ModelsConsideringDefects . . . . . . . . . . . . . . . . . . 110
3.4 III-NitrideDMSMaterials . . . . . . . . . . . . . . . . . . . . . . . . 110
3.4.1 Gd-DopedGaN . . . . . . . . . . . . . . . . . . . . . . . . . 111
3.4.2 Gd-andSi-co-dopedGaN . . . . . . . . . . . . . . . . . . . 112
3.4.3 Gd-DopedAlGaNandHeterostructures . . . . . . . . . . . 115
3.4.4 Gd-ImplantedGaN . . . . . . . . . . . . . . . . . . . . . . . 116
3.4.5 Gd-ImplantedAlGaN/GaNDeviceStructures . . . . . . . 117
3.4.6 Gd-DopedandImplantedAlN . . . . . . . . . . . . . . . . 117
3.5 SummaryandIssuestoBeResolved . . . . . . . . . . . . . . . . . . 117
4. ElectronicStructureofMninIII-Mn-VFerromagneticSemiconductors 123
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
4.2 LatticeSiteLocationofMninGa1−xMnxAs . . . . . . . . . . . . . . 124
4.2.1 Self-compensationandMnLocationinGaMnAs . . . . . . 124
4.2.2 Channeling Rutherford Backscattering and Particle
InducedX-rayEmission . . . . . . . . . . . . . . . . . . . . 125
4.2.3 DetectionofMnInterstitialsinGaMnAs . . . . . . . . . . . 126
4.2.4 StabilityofMnInterstitials . . . . . . . . . . . . . . . . . . . 129
4.2.5 Maximum Carrier Concentration and T in III-Mn-V
C
Semiconductors . . . . . . . . . . . . . . . . . . . . . . . . . 136
4.2.6 Co-dopingofGaMnAswithShallowDopants . . . . . . . . 137
4.3 ElectronicStructureofMninGaMnAs . . . . . . . . . . . . . . . . . 143
4.3.1 ValenceBandAnticrossingModel . . . . . . . . . . . . . . . 146
4.3.2 MobilityandtheMetal-to-InsulatorTransition . . . . . . . 147
4.3.3 Ga1−xMnx-VAlloys . . . . . . . . . . . . . . . . . . . . . . . 151
4.4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
5. Ga1−xMnxPSynthesizedbyIonImplantationandPulsed-LaserMelting 157
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
5.2 IonImplantationandPulsed-LaserMelting(II-PLM) . . . . . . . . 159
5.3 EvidenceoftheCarrier-MediatedPhaseofGa1−xMnxP . . . . . . . 163
5.4 TheDetachedMn-DerivedImpurityBandinGa1−xMnxP . . . . . . 166
5.5 MagneticAnisotropy . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
5.6 ElectricalTransport . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
5.7 StabilityofMnGaDefectinGa1−xMnxP:BehaviorUponExtended
Annealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
5.8 ComparisonofGa1−xMnxPtoOtherIII1−xMnxVMaterials . . . . . 174
5.9 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
6. InMnAsThinFilmsandHeterostructures 181
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
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6.2 EpitaxialFilmDeposition . . . . . . . . . . . . . . . . . . . . . . . . 182
6.3 ElectronicPropertiesofInMnAs . . . . . . . . . . . . . . . . . . . . 184
6.4 MagneticProperties. . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
6.5 MagnetoresistanceandMagnetotransport . . . . . . . . . . . . . . . 185
6.6 BipolarMagneticSemiconductorDeviceStructures . . . . . . . . . 187
6.7 Magneto-opticalProperties . . . . . . . . . . . . . . . . . . . . . . . 189
6.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
7. MagneticDopingofGroupIVSemiconductors 193
7.1 GeneralIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
7.2 Magnetic Doping of Conventional Semiconductors: Theoretical
Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
7.3 Magnetic Doping of Conventional Semiconductors: Practical
Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
7.4 MnxGe1−x: ASiliconCompatibleDMS . . . . . . . . . . . . . . . . 199
7.4.1 MagneticProperties . . . . . . . . . . . . . . . . . . . . . . . 201
7.4.2 TransportProperties . . . . . . . . . . . . . . . . . . . . . . . 205
7.4.3 GeneralizedPolaronPercolationPicture . . . . . . . . . . . 212
7.4.4 UltraDiluteRegimeofMnxGe1−x DMS . . . . . . . . . . . 214
7.5 ConcludingRemarks . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
8. DynamicsofLocalizedSpinsinNon-MagneticSemiconductors 225
8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
8.2 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226
8.3 SpinInitialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
8.4 SpinLifetimes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
8.5 SpinRotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
8.6 ApplicationsI:CoherentPopulationTrapping . . . . . . . . . . . . 235
8.7 ApplicationsII:TransferofLightPolarizationtoSpinCoherence. . 237
8.8 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
9. Zero-BiasSpinSeparation 243
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 243
9.2 MicroscopicModel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
9.2.1 PhotoexcitationMechanismofaPureSpinCurrent . . . . . 245
9.2.2 RelaxationMechanismofaPureSpinCurrent . . . . . . . . 246
9.3 ConversionofPureSpinCurrentintoSpinPhotocurrent . . . . . . 246
9.3.1 SpinPhotocurrentDuetothePhotoexcitationMechanism . 247
9.3.2 SpinPhotocurrentDuetotheRelaxationMechanism . . . . 249
9.3.3 SpinPhotocurrentsinDilutedMagneticSemiconductors . 250
9.3.4 Phenomenological Theory of the Magneto-gyrotropic
PhotogalvanicEffect. . . . . . . . . . . . . . . . . . . . . . . 252
9.4 ExperimentsontheZero-BiasSpinSeparation . . . . . . . . . . . . 253
9.5 ApplicationofSpinPhotocurrents . . . . . . . . . . . . . . . . . . . 258
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9.6 ConcludingRemarks . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
10. Electrical Spin Injection in Hybrid Ferromagnetic
Metal/SemiconductorStructures 265
10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
10.2 TheoryofSpinInjectionThroughaHybridMetal–Semiconductor
Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
10.2.1 TheDiffusiveRegimeofSpinInjectionandtheProblemof
ImpedanceMismatch . . . . . . . . . . . . . . . . . . . . . . 266
10.2.2 MicroscopicPicture . . . . . . . . . . . . . . . . . . . . . . . 270
10.3 MeasurementoftheElectricalSpinInjectioninHybridDevices . . 272
10.3.1 GeneralConsiderations . . . . . . . . . . . . . . . . . . . . . 272
10.3.2 Spin-LEDswithSchottkyBarriers . . . . . . . . . . . . . . . 273
10.3.3 Spin-LEDswithAlumineBarriers . . . . . . . . . . . . . . . 276
10.3.4 Spin-LEDswithMgOBarriers . . . . . . . . . . . . . . . . . 280
10.3.5 Pulsed Electrical Injection and Time-Resolved
Electroluminescence . . . . . . . . . . . . . . . . . . . . . . . 284
10.4 ConclusionsandOutlook . . . . . . . . . . . . . . . . . . . . . . . . 286
11. Magneto-optical Spectroscopy of Spin Injection and Spin
RelaxationinSpinLight-EmittingStructures 289
11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
11.2 SampleStructures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
11.2.1 ZnMnSe/Zn(Cd)SeQWSpinInjectionStructures . . . . . . 290
11.2.2 ZnMnSe/CdSeQDSpinInjectionStructures . . . . . . . . . 290
11.2.3 GaMnN/InGaNSpinLightEmittingDiodeStructures . . . 290
11.2.4 ZnO-BasedStructures . . . . . . . . . . . . . . . . . . . . . . 291
11.3 ZnMnSe/ZnCdSeQWSpinInjectionStructures . . . . . . . . . . . 291
11.3.1 SpinInjection . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
11.3.2 SpinAlignment . . . . . . . . . . . . . . . . . . . . . . . . . 297
11.3.3 SpinDetection . . . . . . . . . . . . . . . . . . . . . . . . . . 304
11.4 SpinPolarizationinZnMnSe/CdSeQDSpinInjectionStructures . 308
11.5 GaMnN/InGaNSpinInjectionStructures . . . . . . . . . . . . . . . 311
11.5.1 SpinInjection . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
11.5.2 SpinDetection . . . . . . . . . . . . . . . . . . . . . . . . . . 312
11.6 ZnO-BasedSpinFunctionalStructures . . . . . . . . . . . . . . . . . 316
11.6.1 SpinDetection: OpticalOrientationMeasurements . . . . . 316
11.6.2 Spin Detection: Time-Resolved Magneto-optical
Spectroscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
11.6.3 Spin Detection: Possible Mechanisms for Spin
Depolarization . . . . . . . . . . . . . . . . . . . . . . . . . . 319
11.7 ConclusionsandOutlook . . . . . . . . . . . . . . . . . . . . . . . . 320
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ColorPlates 325
Index 355