Diluted Magnetic Semiconductors

The following sections are included:

• Contributors

• Introduction

• Contents

The following sections are included:

• INTRODUCTION

• GENERAL PROPERTIES OF HOST MATERIALS
  • The A^II-B^VI Host Binaries
  • The A^IV-B^VI Host Binaries

• CRYSTAL STRUCTURE, LATTICE PARAMETER AND THE BAND GAP OF DMS
  • The DMS
    • Composition Dependence of Crystal Structure and Lattice Parameter
    • Composition Dependence of Energy Gap
  • The DMS
    • Composition Dependence of Crystal Structure and Lattice Parameter
    • Compositional Dependence of Energy Gaps

• PREPARATION OF DMS CRYSTALS

• SOME RECENT DEVELOPMENTS IN DMS
  • The DMS
  • The A_1-xEu_xB DMS
  • DMS Quantum Wells and Superlattices

• REFERENCES

The following sections are included:

• INTRODUCTION

• EXCHANGE INTERACTION IN WIDE-GAP SMSC AT Γ POINT
  • Zeeman splitting in wide-gap Mn-based SMSC
  • Exchange effects in new wide-gap SMSC compounds
  • Theoretical model of Exchange Interaction and approximations in wide-gap SMSC
  • Origin of the sp-d exchange
  • Deviation from Mean Field Model for concentrated Mn-based SMSC compounds

• MAGNETIC CONTRIBUTION TO THE ENERGY GAP OF SMSC

• OPTICAL TRANSITIONS AND ZEEMAN SPLITTING IN THE VINICITY OF THE L POINT OF THE BRILLOUIN ZONE
  • Optical transitions in the vinicity of E_l and E_l+Δ_l
  • Dependence of E_l and E₁+Δ₁ energies with temperature and Manganese composition
  • Zeeman splitting at L point of the Brillouin zone

• REFERENCES

The following sections are included:

• INTRODUCTION

• BASIC CONSIDERATIONS
  • The Forbidden Gap As A Function Of The Mn Concentration
  • The Ground State Of Mn²⁺ In The II-VI Compounds
  • The Dependence Of The Luminescence Upon The Mn Concentration
  • The Selfactivated Luminescence
  • The Time Dependence Of Luminescence Emission

• LUMINESCENCE PROPERTIES OF DIFFERENT WIDE BAND GAP II-Mn-VI SMSCs
  • Zn_1−xMn_xS
    • Emission
    • Excitation
    • Transient measurements
  • Cd_l−xMn_XS
    • Emission
    • Excitation
    • Transient measurements
  • Zn_1−xMn_xSe
    • Emission
    • Excitation
    • Transient measurements
  • Cd_1−xMn_xSe
    • Emission
    • Excitation
  • Zn_1−xMn_xTe
    • Emission
    • Excitation
    • Transient measurements
  • Cd_1−xMn_xTe
    • Emission
    • Excitation
    • Transient measurements

• ON THE NATURE OF THE Mn CORRELATED LUMINESCENCE CENTERS AND CHEMICAL TRENDS

• Acknowledgement

• REFERENCES

The following sections are included:

• INTRODUCTION

• RESULTS OF PHOTOEMISSION SPECTROSCOPY

• PREVIOUS THEORETICAL MODELS
  • One-Electron Models
  • Ligand-Field Theory

• CONFIGURATION-INTERACTION THEORIES
  • Anderson Model and its Relation to Other Models
  • Configuration Interaction Theory

• COMPARISON WITH EXPERIMENTS
  • Photoemission Spectra
  • d-d Optical Absorption
  • Charge-transfer Optical Absorption and Inverse Photoemission
  • Magnetic Interactions

• FIRST-PRINCIPLES ESTIMATION OF THE MODEL PARAMETERS

• CONCLUSION

• ACKNOWLEDGEMENTS

• REFERENCES

A review is given of the numerous effects the sp–d exchange interaction may have upon electron transport phenomena in diluted magnetic semiconductors doped with hydrogenic-like impurities. The ranges of impurity concentrations that correspond to the metallic and to the insulating phases are considered. Particular attention is payed to the transitory region between the above two extreme cases where the metal–insulator transition occurs. In this region the presence of the exchange interaction manifests itself in a rather non–standard way, and constitutes a valuable tool to elucidate the driving mechanisms of the transition. The effects of the giant s–d spin–splitting of electronic levels, the fluctuations of magnetization, and the formation of magnetic polarons are described in detail, while the phenomena associated with long range magnetic ordering, such as electron–magnon interaction, are not discussed as diluted magnetic semiconductors exist almost exclusively in a paramagnetic or spin–glass phase. The theoretical survey is illustrated by experimental results for Mn-based II–VI compounds. The second part of the article concerns such diluted magnetic semiconductors, in which magnetic constituents act as resonant impurities. The remarkable properties of Hg_1−xFe_xSe in the mixed–valence region of Fe donors are presented. An interesting problem of electron localization in the case when the potential of the donating impurity has no bound states is also mentioned. Preceding the discussion of the above issues, basic information concerning the location of energy levels of transition metals in II–VI semiconductors is presented and the various models of the metal–insulator transition in electronic systems are recalled.

The following sections are included:

• INTRODUCTION

• EXPERIMENTAL INVESTIGATIONS
  • Sample Preparation
  • Phase-Transition Studies
    • X-ray Measurements
    • Resistivity Measurements
  • Pressure Variations of Elastic Constants

• THEORETICAL INVESTIGATIONS
  • Pressure Induced Phase-Transition
    • Singh and Prabhakar Method
    • Three-Body Potential Approach
  • Equation of State
  • ANHARMONIC ELASTIC PROPERTIES
    • Third Order Elastic Constants
    • Pressure Derivatives of SOECs

• OVERVIEWS

• ACKNOWLEDGEMENTS

• REFERENCES

The following sections are included:

• INTRODUCTION

• GENERAL PROPERTIES
  • Structure and Lattice Parameters
  • Electronic Band Structure
  • Magnetic Properties
  • Lattice Dynamical Properties

• BASIC CONCEPTS OF RAMAN SPECTROSCOPY
  • Introduction to RS Processes
  • Morphology of Raman Spectra
  • Resonant Raman Scattering
  • Experimental Techniques
    • Frequency scanning mode
    • Diode array detection systems
    • Fourier transform Raman spectroscopy (FTRS)
    • Raman microprobing
    • Waveguide Raman spectroscopy

• RAMAN STUDIES OF (Cd,B)Mn, B=Te, Se, S
  • (Cd,Te)Mn
    • Raman scattering by phonons
    • Magnetic excitations in the paramagnetic phase
    • Magnetic excitations in the ordered phases
  • (Cd,Se)Mn
    • Raman scattering by phonons
    • Magnetic excitations
  • (Cd,S)Mn

• RAMAN STUDIES OF (Zn,B)Mn, B=Te, Se, S
  • (Zn,Te)Mn
  • (Zn,Se)Mn
    • Raman scattering by phonons
    • Magnetic excitations
  • (Zn,S)Mn

• OTHER POSSIBILITIES OF DMS

• CONCLUSION

• Acknowledgments

• REFERENCES

The following sections are included:

• INTRODUCTION

• Mn-BASED SMSC (L=O, S=5/2)
  • MAGNETIC PROPERTIES
    • Experimental Results
      • Specific heat
      • High-temperature susceptibilty
      • Low-temperature susceptibilty
      • Magnetization
    • Spin-glass Phase Transition
    • Single Mn Ion and Mn–Mn Pair (theory)
    • Extended Nearest Neighbour Pair Approximation (ENNPA)
  • OPTICAL PROPERTIES
    • Free Exciton Spectroscopy
    • s-d Exchange In SMCS
    • Bound Magnetic Polaron (BMP)

• Fe-BASED SMSC (L=2, S=2)
  • THE CRYSTALS
  • MAGNETIC PROPERTIES
    • Experimental Data
      • Specific heat
      • Low-temperature susceptibilty
      • High-temperature susceptibilty
      • Magnetization
    • Theoretical Description of the Magnetic Properties
      • Isolated Fe⁺⁺ ion
      • Jahn-Teller coupling
      • High Temperature Expansion series for Fe-based SMSC
      • Theory of an Fe–Fe pair
        • Cubic case
        • Hexagonal case
    • Description of the Paramagnetic Phase of Fe-based SMSC
    • The Nature of d-d Interaction
  • OPTICAL PROPERTIES
    • Far Infrared Spectroscopy
    • IR Intra Ion Transitions
    • Free Exciton Spectroscopy
    • s-d Exchange Interaction for Fe-based SMSC
    • Polaron Effects

• CONCLUDING REMARKS

• Acknowledgement

• References

The following sections are included:

• INTRODUCTION

• MAGNETIC PROPERTIES
  • Susceptibility
  • High Field Magnetization
  • Spin Glass Phase
  • Free Carrier Induced Ferromagnetism
  • Magnetic Properties of Layered IV-VI Diluted Magnetic Semiconductors

• CALCULATION OF LANDAU STATES: MEAN FIELD THEORY FOR IV-VI COMPOUNDS

• MAGNETOTRANSPORT

• OPTICAL INTERBAND TRANSITIONS
  • Photoluminescence Without Magnetic Field
  • Magnetooptical Interband Transitions

• COHERENT RAMAN SCATTERING
  • Theory
    • Classical approach
    • Nonlinear susceptibility in semiconductors
  • Experimental Results and Discussion
    • Results: Pb_1−xMn_xTe
    • Results: Pb_1−xEu_xSe
  • Effective Electron and Hole g factors

• FAR INFRARED SPECTROSCOPY

• COMPARISON EXPERIMENT - MOLECULAR FIELD THEORY
  • Band and Exchange Parameters
  • Selection Rules

• CONCLUSION

• ACKNOWLEDGEMENTS

• REFERENCES

The following sections are included:

• Introduction

• co²⁺ ions in a tetrahedral crystal field
  • Single ion case
  • co²⁺ ion pairs

• Results and analysis
  • Electron paramagnetic resonance
  • Magnetic susceptibility
    • DMS's with the zinc blende lattice: Zn_1−xCo_xS and Zn_1−xCo_xSe
    • DMS's with the wurtzite lattice: Cd_1−xCo_xS and Cd_1−xCo_xSe
    • The spin-glass state
  • Inelastic neutron scattering
  • Specific heat at low temperatures
  • Other experimental results

• Concluding remarks

• Acknowledgments

• REFERENCES

The following sections are included:

• INTRODUCTION

• THE SUBBAND STRUCTURE

• SUBBAND STRUCTURE OF Cd_(1−x) Mn_(x) Te - Cd Te

• THE LANDAU LEVELS OF Cd_(1−x) Mn_(x) Te - Cd Te

• MAGNETIC POLARON EFFECT

• ACKNOWLEDGEMENTS

• REFERENCES

The following sections are included:

• Introduction

• Preparation and Structure Characterization

• Valence and Conduction Band related Properties

• Phonons

• Special Properties due to S,p-Mn²⁺(3d) Exchange Interaction

• Magnetic Phase Transition

• Concluding Remarks

• References

The following sections are included:

• INTRODUCTION

• DMS MATERIALS

• MATERIAL PREPARATION
  • LPE Technique
  • VPE Technique

• DETECTOR PREPARATION
  • A Profile of p-n Junction Detector
  • A p-n Junction Configuration

• DETECTOR PROPERTIES
  • Electrical Properties of DMS Detectors
  • Photoelectric Properties of DMS Detectors

• FINAL COMMENTS

• REFERENCES

The ternary diluted magnetic semiconductors Cd_1−xMn_xTe, Hg_l−yMn_yTe and the quaternary Hg_l−x−yCd_xMn_yTe are used in a variety of optoelectronic devices. The recent literature is reviewed with an emphasis on operation at or near room temperature.

Characteristics of ZnS:Mn phosphor films for ac thin-film electroluminescent (TFEL) devices were examined in detail; the relationships between the crystallographic, microstructural, chemical, and electroluminescent characteristics and the growth mechanism, postannealing temperature, and effects of an oxygen and some metal oxide impurities introduced into the ZnS:Mn phosphor films were clarified.

The following sections are included:

• Introduction

• Some comments on Eu solubility in thin film and bulk II-VI compounds

• Eu charge states and energy structure
  • Eu₂₊ energy structure
  • ESR study of Eu₂₊ in II-VI and europium chalcogenides
  • Eu₂₊ energy level position
  • The concept of RE bound excitons
  • Relation between Eu energy level positions and PL, EL mechanism
  • Energy transfer mechanism of the Eu₂₊ excitation in SrS: Ce, K

• Towards Eu-based diluted magnetic compounds

• Conclusions

• Acknowledgements

• References

The following sections are included:

• Author Index

• Subject index