Book contents
- Frontmatter
- Contents
- Preface
- 1 Introduction
- PART ONE CONCEPTS AND PROPERTIES
- 2 The interaction of radiation with matter
- 3 General properties of the optical constants
- 4 The medium: correlation and response functions
- 5 Metals
- 6 Semiconductors
- 7 Broken symmetry states of metals
- PART TWO METHODS
- PART THREE EXPERIMENTS
- PART FOUR APPENDICES
- Index
6 - Semiconductors
Published online by Cambridge University Press: 20 May 2010
- Frontmatter
- Contents
- Preface
- 1 Introduction
- PART ONE CONCEPTS AND PROPERTIES
- 2 The interaction of radiation with matter
- 3 General properties of the optical constants
- 4 The medium: correlation and response functions
- 5 Metals
- 6 Semiconductors
- 7 Broken symmetry states of metals
- PART TWO METHODS
- PART THREE EXPERIMENTS
- PART FOUR APPENDICES
- Index
Summary
The focus of this chapter is on the optical properties of band semiconductors and insulators. The central feature of these materials is the appearance of a single-particle gap, separating the valence band from the conduction band. The former is full and the latter is empty at zero temperature. The Fermi energy lies between these bands, leading to zero dc conduction at T=0, and to a finite static dielectric constant. In contrast to metals, interband transitions from the valence band to the conduction band are of superior importance, and these excitations are responsible for the main features of the electrodynamic properties. Many of the phenomena discussed in this chapter also become relevant for higher energy excitations in metals when the transition between bands becomes appreciable for the optical absorption.
Following the outline of Chapter 5, we first introduce the Lorentz model, a phenomenological description which, while obviously not the appropriate description of the state of affairs, reproduces many of the optical characteristics of semiconductors. The transverse conductivity of a semiconductor is then described, utilizing the formalisms which we have developed in Chapter 4, and the absorption near the bandgap is discussed in detail, followed by a summary of band structure effects. After discussing longitudinal excitations and the q dependent optical response, we briefly mention indirect transitions and finite temperature and impurity effects; some of the discussion of these phenomena, however, is relegated to Chapter 13.
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- Chapter
- Information
- Electrodynamics of SolidsOptical Properties of Electrons in Matter, pp. 136 - 172Publisher: Cambridge University PressPrint publication year: 2002