CONTENTS Preface I. Energy Band Theory 1. 1. Electron in a crystal 1. 1. 1. Two examples of electron behavior. L1.1. Free electron 1. 2. The particle-in-a-box approach.. 1. 1. 2. Energy bands of a crystal (intuitive approach) 6 1.3. Kronig-Penney model 1 14. Valence band and conduction band 1. 5. Parabolic band approximation 1. 1.6. Concept of a hole 20 1.1.7. Effective mass of the electron in a crystal 1.1.8. Density of states in energy bands…………,25 1. 2. Intrinsic semiconductor 1. 3. Extrinsic semiconductor. 1.3. 1. lonization of impurity atoms. 1.3.2. Electron-hole equilibrium. 1.3.3. Calculation of the Fermi Level 1.3.4. Degenerate semiconductor……… 1. 4. Alignment of Fermi levels Important Equations Problems 2. Theory of Electrical Conduction,…,…,… 2.1. Drift of electrons in an electric field 2.2. Mobility 2.3. Drift current 2.3.1. Hall effect 2,4. Diffusion current 2.5. Drift-diffusion equations 2.5.1. Einst 2.6. Transport equations 2.7. Quasi-Fermi levels 65 Important equations ProblemsCONTENTS Preface 1. Energy Band Theory 1.1. Electron in a crystal 1.1.1. Two examples of electron behavior 1.1.1.1. Free electron 1.1.1.2. The particle-in-a-box approach 1.1.2. 1.1.3. 1.1.4. 1.1.5. 1.1.6. 1.1.7. 1.1.8. Energy bands of a crystal (intuitive approach) Krönig-Penney model Valence band and conduction band Parabolic band approximation Concept of a hole Effective mass of the electron in a crystal Density of states in energy bands 1.2. 1.3. Intrinsic semiconductor Extrinsic semiconductor 1.3.1. 1.3.2. 1.3.3. 1.3.4. Ionization of impurity atoms Electron-hole equilibrium Calculation of the Fermi Level Degenerate semiconductor 1.4. Alignment of Fermi levels Important Equations Problems 2. Theory of Electrical Conduction 2.1. 2.2. 2.3. Drift of electrons in an electric field Mobility Drift current 2.3.1. Hall effect 2.4. 2.5. 2.5.1. 2.6. 2.7. Diffusion current Drift-diffusion equations Einstein relationships Transport equations Quasi-Fermi levels Important Equations Problems xi 1 1 1 1 3 6 7 15 19 20 21 25 29 31 34 35 37 39 40 43 44 51 51 53 56 57 59 60 60 62 65 67 68