In introductory solid-state physics texts we are introduced to the concept of a perfect crystalline solid with every atom in its proper place. This is a convenient first step in developing the concept of electronic band struc­ ture, and from it deducing the general electronic and optical properties of crystalline solids. However, for the student who does not proceed further, such an idealization can be grossly misleading. A perfect crystal does not exist. There are always defects. It was recognized very early in the study of solids that these defects often have a profound effect on the real physical properties of a solid. As a result, a major part of scientific research in solid-state physics has,' from the early studies of "color centers" in alkali halides to the present vigorous investigations of deep levels in semiconductors, been devoted to the study of defects. We now know that in actual fact, most of the interest­ ing and important properties of solids-electrical, optical, mechanical- are determined not so much by the properties of the perfect crystal as by its im­ perfections.

Inhalt

1. Introduction.- 2. Lattice Distortion and the Jahn-Teller Effect.- 2.1 The Electron-Phonon Interaction.- 2.1.1 The Born-Oppenheimer and Related Adiabatic Approximations.- 2.1.2 Electron-Lattice Coupling.- 2.1.3 Occupancy Levels and One-Electron Eigenvalues.- 2.2 Symmetry Considerations: The Stable Atomic Configurations.- 2.2.1 General Reduction of the Jahn-Teller Matrices in Td Symmetry.- 2.2.2 The Stable Distortions.- a) The Nondegenerate A1 (or A2) Level.- b) The Twofold Degenerate Level E.- c) The Triply Degenerate State T Coupled to E Modes.- d) The Triply Degenerate State Coupled to E and T Modes.- 2.2.3 The Case of Near Degeneracy.- 2.3 Coupled Electronic and Nuclear Motion: Vibronic States - Static and Dynamic Jahn-Teller Limits.- 2.3.1 The E State Coupled to E Modes (Case of Cylindrical Symmetry).- 2.3.2 Static and Dynamic Jahn-Teller Effects.- a) The Static Limit.- b) The Dynamic Limit.- 2.3.3 The Ham Effect.- 2.3.4 Extension to More Complex Cases.- a) T2 Level with T2 Modes.- b) E Level with E Modes.- 2.3.5 Transitions from Static to Dynamic Situations.- 2.4 The Vacancy in Silicon.- 2.4.1 Static Distortions Near the Vacancy.- 2.4.2 The Relative Importance of the Many-Electron Effects and the Jahn-Teller Effect.- 2.4.3 Effective Force Constants Near the Vacancy.- 2.4.4 The Negative U Center Formed by V++, V+, V0, in Silicon.- 3. Electron Paramagnetic Resonance.- 3.1 The Hamiltonian.- 3.2 Electronic Zeeman Interaction.- 3.2.1 Zeeman Interaction.- 3.2.2 Spin Resonance.- 3.2.3 Observation of Resonance.- 3.3 Spin Orbit Coubling.- 3.3.1 Quenching of Orbital Motion.- 3.3.2 Effective Spin Hamiltonian.- 3.3.3 Quantitative Treatment of the g Tensor.- 3.3.4 Analysis of the g Tensor.- 3.4 Hyperfine Interaction.- 3.5 Nuclear Zeeman Interaction - Double Resonance.- 3.6 Spin-Spin Interaction. Fine Structure.- 3.7 EPR of Impurities and Vacancy - Impurity Pairs in Silicon.- 3.7.1 Evaluation of the g Shift.- 3.7.2 The Hyperfine Tensor.- 3.7.3 Experimental Results.- 3.8 The Vacancy in Silicon.- 3.8.1 EPR Spectrum for V+.- 3.8.2 Microscopic Model for V+.- 3.8.3 Charge States of the Vacancy.- 3.8.4 Jahn-Teller Distortion.- 3.8.5 Energy Levels.- 4. Optical Properties.- 4.1 Transition Probability.- 4.2 The Configuration Coordinate Diagram.- 4.3 Optical Line Shape and the Electron-Lattice Interaction.- 4.3.1 Coupling to One Lattice Coordinate at T = 0 K.- 4.3.2 Overlap Between Harmonic Oscillators.- 4.3.3 The Low-Temperature Limit.- 4.3.4 The Strong Coupling Limit.- 4.3.5 Classical Treatment for the Lattice.- 4.3.6 Coupling to a Continuum of Lattice Modes.- 4.3.7 Moments of the Line-Shape Function.- 4.4 Optical Cross Section.- 4.4.1 Theoretical Models.- 4.4.2 Exact Expression for the Case of a Delta-Function Potential.- 4.4.3 Measurement.- 4.5 An Example. The GR Absorption Band in Diamond.- 4.5.1 Experimental Situation.- 4.5.2 Theoretical Interpretation.- 5. Electrical Properties.- 5.1 Carrier Distribution Between Bands and Defect Levels.- 5.1.1 Intrinsic Semiconductor.- 5.1.2 Extrinsic Semiconductor.- 5.1.3 The Degeneracy Factor.- 5.1.4 Experimental Determination of Defect Concentration.- 5.2 Conduction in Case of Defect Interaction.- 5.2.1 Metallic Conduction.- 5.2.2 Hopping Conduction.- a) Jump Probability.- b) Hopping Conductivity.- 5.2.3 Observation of Hopping Conductivity.- 5.3 Carrier Scattering.- 5.3.1 Scattering Cross Section.- 5.3.2 Mobility.- a) Scattering by a Charged Center.- b) Scattering by Pairs.- c) Scattering by Neutral Defects.- 5.3.3 Experimental Results.- 6. Carrier Emission and Recombination.- 6.1 Emission and Capture Rates.- 6.1.1 The Principle of Detailed Balance.- 6.1.2 Enthalpy and Entropy of Ionization.- 6.1.3 Trapping and Recombination Centers.- 6.2 Experimental Observation of Emission Rates.- 6.2.1 Principle.- 6.2.2 Observation Techniques.- 6.2.3 Emission from Minority and Majority Carrier Traps.- 6.2.4 Capture and Reemission from Majority Carrier Traps.- 6.2.5 Exact Theory.- 6.2.6 Deep Level Transient Spectroscopy.- 6.2.7 Admittance Spectroscopy.- 6.3 Nonradiative Recombination Processes.- 6.3.1 Auger Processes.- 6.3.2 Cascade Capture.- 6.3.3 Carrier Capture by Multiphonon Emission.- 6.4 Experimental Determination of Ionization Energies, Entropies and Cross Sections.- 6.4.1 Capture Cross Section.- 6.4.2 Experimental Determination of Ionization Energies and Entropies.- 6.4.3 DLTS Observation of a Negative U Center: The Vacancy in Silicon.- 6.5 Influence of the Electric Field on Emission Rates.- 6.5.1 The Frenkel-Poole Effect.- 6.5.2 Tunnelling Effect.- 6.5.3 Phonon-Assisted Tunnel Emission.- 7. Other Methods of Detection.- 7.1 Photoexcitation.- 7.1.1 Principle.- 7.1.2 Shockley-Read Recombination.- 7.1.3 Photoconductivity.- 7.1.4 Spin-Dependent Recombination.- 7.1.5 An Example: Photoconductivity of Boron in Diamond.- 7.2 Optical Detection of Paramagnetic Resonance.- 7.2.1 Principle of the Technique.- 7.2.2 ODMR of Deep Donor-Acceptor Pairs.- 7.3 Direct Detection of Phonons.- 7.3.1 Calorimetric Absorption.- 7.3.2 Photoacoustic Spectroscopy.- 8. Defect Production by Irradiation.- 8.1 Interaction of Radiation with Solids.- 8.1.1 General Formalism.- 8.1.2 Dynamics of a Collision.- 8.1.3 Differential Scattering Cross Section.- a) Hard Sphere Collision.- b) Rutherford Scattering.- 8.2 Defect Production.- 8.2.1 Displacement of the Primary Knock-On Atom.- 8.2.2 Threshold Energy for Atomic Displacement.- 8.2.3 Primary Displacements.- a) Heavy Charged Particles (Ions).- b) Neutrons.- c) Electrons.- 8.2.4 Secondary Displacements.- 8.3 Defect Nature and Spatial Distribution.- 8.3.1 Average Number of Defects per Particle.- 8.3.2 Amorphous Layer Formation by Irradiation.- 8.3.3 Range of the Particle.- 8.4 Experimental Determination of a Threshold Energy.- 8.5 Subthreshold Effects.- 9. Defect Annealing.- 9.1 Annealing Kinetics.- 9.1.1 Rate of Reaction.- 9.1.2 Order of Reaction.- 9.1.3 Description in Terms of Chemical Reactions.- 9.1.4 Recombination of Correlated Pairs.- 9.2 Determination of the Annealing Parameters.- 9.2.1 Rate Constant and Order of Reaction.- 9.2.2 Isothermal Annealing.- 9.2.3 Isochronal Annealing.- 9.3 Annealing of Defects Induced by Electron Irradiation.- 9.3.1 Stability of the Vacancy-Interstitial Pair.- 9.3.2 Mechanism for Complex Defect Formation.- 9.3.3 On the Mobility of the Interstitial.- 9.3.4 An Example: The Case of Silicon.- References.