Electron Spectrum of Gapless Semiconductors

ISBN-13: 9783642643910 / Angielski / Miękka / 2011 / 249 str.

J. Tsidilkovski

Opis

A presentation of the peculiarities of the physical properties of a comparatively new class of solids. GSs are of practical interest since they are very sensitive to impurities, and to the influence of light, magnetic and electric fields, and to pressure.

Spis treści

1. Introduction.- 2. Band-Structure Calculation Methods.- 2.1 Adiabatic Approximation.- 2.2 The One-Electron Hartree-Fock Approximation.- 2.2.1 The Hartree Approximation.- 2.2.2 The Hartree-Fock Method.- 2.2.3 Discrete Distribution.- 2.3 Correlation Phenomena.- 2.3.1 The Drude-Sommerfeld Gas of Free Electrons.- 2.3.2 Binding Energy.- 2.3.3 Correlation Energy.- 2.4 Methods Used to Solve the Schrödinger Equation.- 2.4.1 General Concept.- 2.4.2 Cellular Method.- 2.4.3 Variational Methods.- 2.4.4 Classification of Computational Methods.- 2.4.5 Tight-Binding Method.- 2.4.6 The APW and KKR Methods.- 2.4.7 OPW and Pseudopotential Methods.- 2.4.8 Linear Methods.- 2.4.9 The k p-Method.- 3. Insulators, Semiconductors, Metals.- 3.1 The Detection of the Gapless State.- 3.1.1 The Very-Small Gap in HgTe.- 3.1.2 The Intrinsic Gapless Semiconductor.- 3.2 Gray Tin.- 3.2.1 Crystal Structure.- 3.2.2 Original Band Schemes.- 3.2.3 Inverse Band Model for ?-Sn.- 3.2.4 Experimental Confirmations of the Inverse-Band Model.- 3.3 Mercury Chalcogenides HgTe and HgSe.- 3.3.1 Crystal Structure and Herman´s Perturbation Method.- 3.3.2 Inverse-Band Model for II-VI Crystals.- 3.3.3 Experimental Confirmations of the Inverse-Band Model.- 3.3.4 The Role of Relativistic Effects.- 3.3.5 Shape of the Energy Bands Near the Edge k = 0.- 3.3.6 Effect of the Electron-Electron Interaction.- 3.3.7 Rearrangement of the Band Structure Subject to a Magnetic Field.- 3.3.8 Rearrangement of the Band Structure Under the Influence of a Hydrostatic Pressure.- 4. Impurities.- 4.1 The Problem of Residual Electron Concentration.- 4.2 Impurities and Intrinsic Defects in Mercury Chalcogenides..- 4.3 Energies of Impurity States.- 4.3.1 Features Peculiar to the Localization of Impurity Levels.- 4.3.2 Energy and Wave Functions of an Electron (Hole) at an Impurity Center.- 4.3.3 Experimental Data for the Binding Energy ?A in HgCdTe Gapless Semiconductors.- 4.3.4 Short-Range Potential.- 4.3.5 Experimental Data for the Binding Energy ?A in HgCdTe Narrow-Gap Semiconductors.- 4.4 Metal-Insulator Transitions.- 4.4.1 Doped Semiconductors.- 4.4.2 The Mott Transition.- 4.4.3 The Anderson Transition.- 4.5 The Mott Transition in n-Type Crystals.- 4.6 The Influence of Compensation on the Mott Transition.- 4.7 An "Anomaly" in the Temperature Dependence of the Electron Concentration.- 4.8 Freeze-Out of Electrons onto Acceptors in a Magnetic Field.- 4.9 Freeze-Out of Electrons onto Acceptors Subject to Hydrostatic Pressure.- 4.10 On the Mobility of Holes in Gapless HgCdTe Crystals.- 5. Semimagnetic Semiconductors.- 5.1 HgMnTe Crystals.- 5.1.1 Peculiarities of Crystalline and Band Structures.- 5.1.2 Magnetic Properties.- 5.1.3 Exchange Interaction.- 5.1.4 Shubnikov-de Haas Oscillations.- 5.1.5 Magnetoresistance.- 5.2 HgSe:Fe Crystals.- 5.2.1 Resonance Donor States of Iron.- a) Spatial Correlation of Charged Fe3+Donors.- b) Experimental Evidence Confirming the Existence of Two Charge States of Fe in HgSe.- c) Anomalies of the HgSe:Fe Properties.- d) The Hall Effect.- e) Stabilization of the Fermi Level.- f) Stabilization of the Electron Concentration with Time.- g) Temperature Variation of the Electron Concentration.- h) Fermi-Level Variations in HgFeSe Doped with Cadmium and Tellurium.- i) Quantum Oscillations.- 5.2.2 Electron Scattering in HgSe:Fe.- a) Anomalies of the Electron Mobility and the Dingle Temperature.- b) Resonance Electron Scattering.- c) Mycielski´s Ordering Model.- d) Analysis of Mycielski´s Ordering Model.- e) Consideration of Disorder in the System of Fe3+Ions.- f) Effect of Vibrations and Non-Ideality of the Wigner Charge Lattice on the Temperature Dependence of the Electron Mobility.- g) A Quantitative Analysis of the Variation in the Electron Mobility when HgSe is Doped with Iron.- 5.3 HgSe:Cr Crystals.- 5.4 DX Centers.- 5.5 The Improved Short-Range Correlation Model.- 6. Conclusion.- 6.1 Practical Applications of Gapless Semiconductors.- 6.2 Some Results and Problems.- References.

Blurb

Electron Spectrum of Gapless Semiconductors presents the peculiarities of physical properties of a comparatively new class of solids - gapless semiconductors (GS). These peculiarities are determined by the main feature of the elctron spectrum, namely the absence of a gap between the conduction and valence bands. GSs form a boundary between metals and semiconductors. On the other hand GSs are of practical interest since they are very sensitive to impurities, and to the influence of light, magnetic and electric fields, and pressure.