Amorphous Silicon

by Tanaka, Kazunobu; Maruyama, Eiichi; Shimada, Toshikazu; Okamoto, Hiroaki

• ISBN13: 9780471982937
• ISBN10: 0471982938
• Edition: 1st
• Format: Hardcover
• Copyright: 1999-03-12
• Publisher: WILEY

Summary

Amorphous Silicon Kazunobu Tanaka National Institute for Advanced Interdisciplinary Research, Ibaraki, Japan Eiichi Maruyama Hitachi Ltd, Ibaraki, Japan Toshikazu Shimada Hitachi Ltd, Ibaraki, Japan Hiroaki Okamoto Osaka University, Osaka, Japan Translated by Takeshi Sato, National Institute for Advanced Interdisciplinary Research, Ibaraki, Japan Amorphous silicon has substantially different properties as compared to crystalline silicon. It has therefore become recognized as a fascinating and important material in its own right, with many interesting facets that lead to a range of novel and still developing applications. Amorphous Silicon introduces the reader to this field by first discussing what is meant by the amorphous state. It details the way in which amorphous silicon is prepared, and the growth mechanism. The main structural, optical and electronic properties are then covered in detail, and there is a full chapter on the structural stability of the material, including photoinduced effects. Finally, a number of the most exciting applications of amorphous silicon are presented, including its use in solar cells, photo-sensors and liquid crystal displays. Amorphous Silicon will be of great interest to all those working in solid state physics or chemistry, materials science and electronic engineering, from postgraduate students to more experienced workers in these fields.

Author Biography

Kazunobu Tanaka is the author of Amorphous Silicon, published by Wiley.

Table of Contents

Preface to the Japanese Edition	ix	(4)
Preface to the English Edition	xiii
1 Introduction	1	(26)
1.1 What is the Amorphous State?	1	(9)
1.1.1 Definition of Terms	1	(1)
1.1.2 The Thermodynamic State	2	(3)
1.1.3 Structural Disorder	5	(3)
1.1.4 Classification of Amorphous Semiconductors	8	(2)
1.2 A Short History of Amorphous Semiconductor Studies	10	(14)
1.2.1 Pioneering Work	10	(7)
1.2.2 Advent of Hydrogenated Amorphous Silicon	17	(4)
1.2.3 Academic Societies and Communities	21	(3)
1.3 Organization of the Book	24	(1)
References	25	(2)
2 Methods of Preparation and Growth Processes	27	(31)
2.1 Outline of Preparative Methods	27	(10)
2.1.1 Non-Equilibrium Processes and Amorphous Structures	27	(4)
2.1.2 Preparation of Amorphous Silicon	31	(6)
2.2 Formation of SiH(4) Plasma	37	(10)
2.2.1 Plasma Reactor Construction and Electron Energy Distribution	37	(2)
2.2.2 Electron Impact Dissociation of SiH(4)	39	(2)
2.2.3 Steady-State Conditions of the SiH(4) Plasma: Merits of Plasma Diagnosis	41	(6)
2.3 Growth Mechanisms	47	(9)
2.3.1 Lifetimes and Diffusion of Species in the SiH(4) Plasma	47	(1)
2.3.2 Adsorption/Desorption of Species and Growth Rates	48	(4)
2.3.3 Surface-Process Model	52	(1)
2.3.4 Surface Diffusion and Network Structure	53	(3)
References	56	(2)
3 Structural Properties	58	(45)
3.1 Morphology (Macroscopic Aspects)	58	(2)
3.2 Hydrogen in a-Si:H Films	60	(8)
3.2.1 Silicon-Hydrogen Bond Types	60	(3)
3.2.2 Spatial Distribution of Hydrogen	63	(4)
3.2.3 Thermal Stability of Hydrogen	67	(1)
3.3 Density	68	(3)
3.3.1 Hydrogen-Free Amorphous Silicon	68	(1)
3.3.2 Hydrogenated Amorphous Silicon	69	(2)
3.4 Structural Order	71	(8)
3.4.1 Amorphous Structure and Hierarchy of Order	71	(1)
3.4.2 Hydrogen-Free Amorphous Silicon	72	(3)
3.4.3 Hydrogenated Amorphous Silicon	75	(4)
3.5 Defects	79	(16)
3.5.1 Concepts and Classification of Defects	79	(3)
3.5.2 Electron Spin Resonance Spectroscopy Studies: Dangling Bonds Versus Floating Bonds	82	(3)
3.5.3 Defect Density and Hydrogen in Films	85	(4)
3.5.4 Thermal Equilibrium Process in Defect Formation	89	(6)
3.6 Impurities	95	(1)
3.7 Doping	96	(4)
3.7.1 Doping Characteristics and Efficiencies: Phosphorus and Boron	96	(2)
3.7.2 Hydrogen in Doped a-Si:H	98	(1)
3.7.3 Electron Spin Resonance Studies	99	(1)
References	100	(3)
4 Optical and Electrical Properties	103	(84)
4.1 Disorder and Electronic Structure	103	(15)
4.1.1 Electronic Structure of Amorphous Semiconductors	103	(2)
4.1.2 Conduction Band and Valence Band	105	(2)
4.1.3 Electronic State Near the Band Edge	107	(4)
4.1.4 Localized Levels Based on Structural Defects	111	(7)
4.2 Structure of the Optical Absorption Edge	118	(14)
4.2.1 Features of the Optical Absorption Spectrum	118	(2)
4.2.2 Inter-Band Transition Region	120	(4)
4.2.3 Band-Tail Transition	124	(4)
4.2.4 Optical Transitions Caused by Structural Defects	128	(4)
4.3 Electrical Properties	132	(15)
4.3.1 Mechanism of Electrical Conduction	132	(4)
4.3.2 DC Conductivity and Thermoelectric Power	136	(4)
4.3.3 Hall Effect	140	(2)
4.3.4 Impurity Doping Effect	142	(5)
4.4 Transport and Recombination of Excess Carrier	147	(21)
4.4.1 Carrier Capture and Non-Radiative Recombination	147	(3)
4.4.2 Recombination and Photoconductivity Under Steady Illumination Conditions	150	(5)
4.4.3 Carrier Transport Characteristics Under Transient Illumination Conditions	155	(4)
4.4.4 Mobility and Lifetime of Carriers	159	(7)
4.4.5 Photoluminescence	166	(2)
4.5 Silicon Alloy Materials and Multilayer Film Properties	168	(11)
4.5.1 Basic Properties of Silicon Alloy Materials	168	(2)
4.5.2 Properties of Multilayer Films	170	(9)
References	179	(8)
5 Structural Stability and Photo-Induced Effects	187	(31)
5.1 Nature of the Non-Equilibrium Solid	187	(2)
5.2 Photo-Induced Effects in Amorphous Semiconductors	189	(5)
5.2.1 Photodarkening and Photostructural Changes	189	(1)
5.2.2 Photo-Induced Metastable ESR Centers	189	(3)
5.2.3 Structural Origins of Photo-Induced Metastability	192	(2)
5.3 The Staebler-Wronski Effect	194	(14)
5.3.1 Description of the Phenomenon	194	(3)
5.3.2 Aspects of Kinetics	197	(3)
5.3.3 Structural Origins and Mechanisms of Defect Formation: Microscopic Models	200	(5)
5.3.4 Phosphorus-Doped a-Si:H	205	(3)
5.4 Thermal Stability	208	(7)
5.4.1 Diffusion and Desorption of Hydrogen and Crystallization of Amorphous Films	208	(4)
5.4.2 Crystallization Processes in Multilayer Films	212	(3)
References	215	(3)
6 Applications	218	(36)
6.1 Features and Applications of Amorphous Semiconductors	218	(6)
6.2 Examples of Applications of Amorphous Semiconductors	224	(29)
6.2.1 Solar Cells	224	(7)
6.2.2 Solid-State Photosensors	231	(5)
6.2.3 Field-Effect (Thin-Film) Transistors for Liquid Crystal Displays	236	(6)
6.2.4 Photoreceptor Drums for Electrophotography and Laser-Beam Printers	242	(3)
6.2.5 Amorphous Selenium Vidicon-Type Image Pick-Up Tubes	245	(8)
References	253	(1)
Index	254