Amorphous Semiconductors

Kazuo Morigaki, Professor Emeritus, University of Tokyo. Morigaki received his Ph.D. degree in physics from Osaka University in 1959. Since then, he has joined Osaka University, Sony Corporation Research Laboratory, Centre d’Etudes Nuclèares de Saclay, University of Tokyo (Institute for Solid State Physics), Yamaguchi University and Hiroshima Institute of Technology. Sandor Kugler, Associate Professor, Department of Theoretical Physics, Budapest University of Technology and Economics, Hungary. Kugler received both his degree in and his PhD in physics from ELTE, Budapest. He  joined the quantum theory group, Institute of Physics, Technical University of Budapest, during 1974-1993 as research associate. Since 1993, he has been Associate Professor.Koichi Shimakawa, Professor Emeritus and Fellow, Gifu University, Japan. Shimakawa received his PhD from Nagoya University in 1975. Since then, he has been at Gifu University, becoming  Professor in the period 1989-2008. He retired from Gifu University in 2008, and is senior researcher, Nagoya Industrial Science Institute, Nagoya, and visiting Professor, Department of Chemistry, University of Pardubice, Czech Republic.

• Series Preface xiPreface xiii1 Introduction 11.1 General Aspects of Amorphous Semiconductors 11.2 Chalcogenide Glasses 31.3 Applications of Amorphous Semiconductors 3References 32 Preparation Techniques 52.1 Growth of a‐Si:H Films 52.1.1 PECVD Technique 52.1.2 HWCVD Technique 62.2 Growth of Amorphous Chalcogenides 6References 83 Structural Properties of Amorphous Silicon and Amorphous Chalcogenides 113.1 General Aspects 113.1.1 Definitions of Crystalline and Noncrystalline 113.2 Optical Spectroscopy 123.2.1 Raman Scattering 123.2.2 Infrared Absorption 133.3 Neutron Diffraction 153.3.1 Diffraction Measurements on Amorphous Silicon 173.3.2 Diffraction Measurements on Hydrogenated Amorphous Silicon 183.3.3 Diffraction Measurements on Amorphous Germanium 193.3.4 Diffraction Measurements on Amorphous Selenium 193.4 Computer Simulations 203.4.1 Monte Carlo‐Type Methods for Structure Derivation 203.4.2 Atomic Interactions 213.4.3 a‐Si Models Constructed by Monte Carlo Simulation 253.4.4 Reverse Monte Carlo Methods 263.4.5 a‐Si Model Constructed by RMC Simulation 283.4.6 a‐Se Model Constructed by RMC Simulation 303.4.7 Molecular Dynamics Simulation 323.4.8 a‐Si Model Construction by Molecular Dynamics Simulation 343.4.9 a‐Si:H Model Construction by Molecular Dynamics Simulation 343.4.10 a‐Se Model Construction by Molecular Dynamics Simulation 353.4.11 Car and Parrinello Method 38References 384 Electronic Structure of Amorphous Semiconductors 434.1 Bonding Structures 434.1.1 Bonding Structures in Column IV Elements 444.1.2 Bonding Structures in Column VI Elements 454.2 Electronic Structure of Amorphous Semiconductors 464.3 Fermi Energy of Amorphous Semiconductors 474.4 Differences between Amorphous and Crystalline Semiconductors 494.5 Charge Distribution in Pure Amorphous Semiconductors 494.6 Density of States in Pure Amorphous Semiconductors 524.7 Dangling Bonds 544.8 Doping 57References 585 Electronic and Optical Properties of Amorphous Silicon 615.1 Introduction 615.2 Band Tails and Structural Defects 625.2.1 Introduction 625.2.2 Band Tails 625.2.3 Structural Defects 665.3 Recombination Processes 685.3.1 Introduction 685.3.2 Radiative Recombination 685.3.3 Nonradiative Recombination 705.3.4 Recombination Processes and Recombination Centers in a‐Si:H 725.3.5 Spin‐Dependent Recombination 735.4 Electrical Properties 745.4.1 DC Conduction 745.4.2 AC Conduction 805.4.3 Hall Effect 875.4.4 Thermoelectric Power 885.4.5 Doping Effect 895.5 Optical Properties 925.5.1 Fundamental Optical Absorption 925.5.2 Weak Absorption 945.5.3 Photoluminescence 965.5.4 Frequency‐Resolved Spectroscopy (FRS) 965.5.5 Photoconductivity 1015.5.6 Dispersive Photoconduction 1095.6 Electron Magnetic Resonance and Spin‐Dependent Properties 1125.6.1 Introduction 1125.6.2 Electron Magnetic Resonance 1125.6.3 Spin‐Dependent Properties 1285.7 Light‐Induced Phenomena and Light‐Induced Defect Creation 1315.7.1 Introduction 1315.7.2 Light‐Induced Phenomena 1325.7.3 Light‐Induced Defect Creation 134References 1456 Electronic and Optical Properties of Amorphous Chalcogenides 1576.1 Historical Overview of Chalcogenide Glasses 1576.1.1 Applications 1576.1.2 Science 1586.2 Basic Glass Science 1596.2.1 Glass Formation 1596.2.2 Glass Transition Temperature 1606.2.3 Crystallization of Glasses 1626.3 Electrical Properties 1656.3.1 Electronic Transport 1656.3.2 Ionic Transport 1706.4 Optical Properties 1756.4.1 Fundamental Optical Absorption 1756.4.2 Urbach and Weak Absorption Tails 1786.4.3 Photoluminescence 1796.4.4 Photoconduction 1836.5 The Nature of Defects, and Defect Spectroscopy 1916.5.1 Electron Spin Resonance 1966.5.2 Optical Absorption 1976.5.3 Primary Photoconductivity 1976.5.4 Secondary Photoconductivity 1976.5.5 Electrophotography 1996.5.6 Electronic Transport 1996.6 Light‐Induced Effects in Chalcogenides 2006.6.1 Electron Spin Resonance 2006.6.2 Optical Absorption 2026.6.3 Photoluminescence 2036.6.4 Photoconductivity 2056.6.5 Electronic Transport 2066.6.6 Defect Creation Kinetics 2076.6.7 Structure‐Related Properties 210References 2187 Other Amorphous Material Systems 2317.1 Amorphous Carbon and Related Materials 2317.1.1 Basic Structure of a‐C (sp2 Hybrids) 2327.1.2 Preparation Techniques 2337.1.3 Brief Review of Structural Studies on Amorphous Carbon 2337.1.4 Applications 2347.2 Amorphous Oxide Semiconductors 2357.2.1 Preparation Techniques 2357.2.2 Optical Properties 2367.2.3 Electronic Properties 2377.2.4 Applications 2397.3 Metal‐Containing Amorphous Chalcogenides 2397.3.1 Preparation Techniques 2407.3.2 Structure of Ag‐Chs and Related Physical Properties 2407.3.3 Photodoping 2417.3.4 Applications 242References 2428 Applications 2478.1 Devices Using a‐Si:H 2478.1.1 Photovoltaics 2478.1.2 Thin‐Film Transistors 2488.2 Devices Using a‐Chs 2498.2.1 Phase‐Change Materials 2498.2.2 Direct X‐ray Image Sensors for Medical Use 2578.2.3 High‐Gain Avalanche Rushing Amorphous Semiconductor Vidicon 2588.2.4 Optical Fibers and Waveguides 260References 261Index 265