Amorphous Oxide Semiconductors
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Amorphous Oxide Semiconductors
IGZO and Related Materials for Display and Memory
Hosono, Hideo; Kumomi, Hideya
John Wiley & Sons Inc
06/2022
640
Dura
Inglês
9781119715573
15 a 20 dias
1558
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Preface xv
Series Editor's Foreword xvii
About the Editors xviii
List of Contributors xix
Part I Introduction 1
1.1 Transparent Amorphous Oxide Semiconductors for Display Applications 3
Hideo Hosono
1.1.1 Introduction to Amorphous Semiconductors as Thin-Film Transistor (TFT) Channels 3
1.1.2 Historical Overview 4
1.1.3 Oxide and Silicon 6
1.1.4 Transparent Amorphous Oxide Semiconductors 6
1.1.4.1 Electronic Structures 6
1.1.4.2 Materials 8
1.1.4.3 Characteristic Carrier Transport Properties 9
1.1.4.4 Electronic States 10
1.1.5 P-Type Oxide Semiconductors for Display Applications 13
1.1.5.1 Oxides of Transition Metal Cations with an Electronic Configuration of (n?1)d 10 ns 0 (n = 4or5) 13
1.1.5.2 Oxides of Metal Cations with an Electronic Configuration of ns 2 13
1.1.5.3 Oxides of Metal Cations with an Electronic Configuration of nd 6 14
1.1.6 Novel Amorphous Oxide Semiconductors 15
1.1.7 Summary and Outlook 17
References 18
1.2 Transparent Amorphous Oxide Semiconductors 21
Hideya Kumomi
1.2.1 Introduction 21
1.2.2 Technical Issues and Requirements of TFTs for AM-FPDs 21
1.2.2.1 Field-Effect Mobility 21
1.2.2.2 Off-State Leakage Current and On/Off Current Ratio 23
1.2.2.3 Stability and Reliability 23
1.2.2.4 Uniformity 23
1.2.2.5 Large-Area Devices by Large-Area Mother-Glass Substrates 24
1.2.2.6 Low-Temperature Fabrication and Flexibility 24
1.2.3 History, Features, Uniqueness, Development, and Applications of AOS-TFTs 24
1.2.3.1 History 24
1.2.3.2 Features and Uniqueness 25
1.2.3.3 Applications 27
1.2.3.4 Development and Products of AM-FPDs 28
1.2.4 Summary 29
References 30
Part II Fundamentals 31
2 Electronic Structure and Structural Randomness 33
Julia E. Medvedeva, Bishal Bhattarai, and D. Bruce Buchholz
2.1 Introduction 33
2.2 Brief Description of Methods and Approaches 35
2.2.1 Computational Approach 35
2.2.2 Experimental Approach 36
2.3 The Structure and Properties of Crystalline and Amorphous In 2 O 3 36
2.4 The Structure and Properties of Crystalline and Amorphous SnO 2 43
2.5 The Structure and Properties of Crystalline and Amorphous ZnO 46
2.6 The Structure and Properties of Crystalline and Amorphous Ga 2 O 3 52
2.7 Role of Morphology in Structure-Property Relationships 57
2.8 The Role of Composition in Structure-Property Relationships: IGO and IGZO 64
2.9 Conclusions 69
References 70
3 Electronic Structure of Transparent Amorphous Oxide Semiconductors 73
John Robertson and Zhaofu Zhang
3.1 Introduction 73
3.2 Mobility 73
3.3 Density of States 74
3.4 Band Structures of n-Type Semiconductors 78
3.5 Instabilities 81
3.6 Doping Limits and Finding Effective Oxide Semiconductors 86
3.7 OLED Electrodes 88
3.8 Summary 89
References 89
4 Defects and Relevant Properties 93
Toshio Kamiya, Kenji Nomura, Keisuke Ide, and Hideo Hosono
4.1 Introduction 93
4.2 Typical Deposition Condition 93
4.3 Overview of Electronic Defects in AOSs 94
4.4 Origins of Electron Donors 96
4.5 Oxygen- and Hydrogen-Related Defects and Near-VBM States 98
4.6 Summary 102
References 102
5 Amorphous Semiconductor Mobility Physics and TFT Modeling 105
John F. Wager
5.1 Amorphous Semiconductor Mobility: An Introduction 105
5.2 Diffusive Mobility 106
5.3 Density of States 110
5.4 TFT Mobility Considerations 111
5.5 TFT Mobility Extraction, Fitting, and Model Validation 112
5.6 Physics-Based TFT Mobility Modeling 118
5.7 Conclusions 121
References 122
6 Percolation Description of Charge Transport in Amorphous Oxide Semiconductors: Band Conduction Dominated by Disorder 125
A. V. Nenashev, F. Gebhard, K. Meerholz, and S. D. Baranovskii
6.1 Introduction 125
6.2 Band Transport via Extended States in the Random-Barrier Model (RBM) 126
6.2.1 Deficiencies of the Rate-Averaging Approach: Electrotechnical Analogy 127
6.2.2 Percolation Approach to Charge Transport in the RBM 129
6.3 Random Band-Edge Model (RBEM) for Charge Transport in AOSs 131
6.4 Percolation Theory for Charge Transport in the RBEM 133
6.4.1 From Regional to Global Conductivities in Continuum Percolation Theory 133
6.4.2 Averaging Procedure by Adler et al. 135
6.5 Comparison between Percolation Theory and EMA 136
6.6 Comparison with Experimental Data 137
6.7 Discussion and Conclusions 140
6.7.1 Textbook Description of Charge Transport in Traditional Crystalline Semiconductors (TCSs) 140
6.7.2 Results of This Chapter for Charge Transport in Amorphous Oxide Semiconductors (AOSs) 141
Acknowledgments 141
References 141
7 State and Role of Hydrogen in Amorphous Oxide Semiconductors 145
Hideo Hosono and Toshio Kamiya
7.1 Introduction 145
7.2 Concentration and Chemical States 145
7.3 Carrier Generation and Hydrogen 150
7.3.1 Carrier Generation by H Injection at Low Temperatures 150
7.3.2 Carrier Generation and Annihilation by Thermal Treatment 151
7.4 Energy Levels and Electrical Properties 153
7.5 Incorporation and Conversion of H Impurities 154
7.6 Concluding Remarks 155
Acknowledgments 156
References 156
Part III Processing 159
8 Low-Temperature Thin-Film Combustion Synthesis of Metal-Oxide Semiconductors: Science and Technology 161
Binghao Wang, Wei Huang, Antonio Facchetti, and Tobin J. Marks
8.1 Introduction 161
8.2 Low-Temperature Solution-Processing Methodologies 162
8.2.1 Alkoxide Precursors 162
8.2.2 Microwave-Assisted Annealing 165
8.2.3 High-Pressure Annealing 165
8.2.4 Photonic Annealing 165
8.2.4.1 Laser Annealing 166
8.2.4.2 Deep-Ultraviolet Illumination 168
8.2.4.3 Flash Lamp Annealing 170
8.2.5 Redox Reactions 170
8.3 Combustion Synthesis for MO TFTs 171
8.3.1 n-Type MO TFTs 172
8.3.2 p-Type MO TFTs 178
8.4 Summary and Perspectives 180
Acknowledgments 180
References 181
9 Solution-Processed Metal-Oxide Thin-Film Transistors for Flexible Electronics 185
Hyun Jae Kim
9.1 Introduction 185
9.2 Fundamentals of Solution-Processed Metal-Oxide Thin-Film Transistors 187
9.2.1 Deposition Methods for Solution-Processed Oxide Semiconductors 187
9.2.1.1 Coating-Based Deposition Methods 190
9.2.1.2 Printing-Based Deposition Methods 191
9.2.2 The Formation Mechanism of Solution-Processed Oxide Semiconductor Films 194
9.3 Low-Temperature Technologies for Active-Layer Engineering of Solution-Processed Oxide TFTs 196
9.3.1 Overview 196
9.3.2 Solution Modulation 197
9.3.2.1 Alkoxide Precursors 198
9.3.2.2 pH Adjustment 199
9.3.2.3 Combustion Reactions 199
9.3.2.4 Aqueous Solvent 199
9.3.3 Process Modulation 201
9.3.3.1 Photoactivation Process 201
9.3.3.2 High-Pressure Annealing (HPA) Process 202
9.3.3.3 Microwave-Assisted Annealing Process 204
9.3.3.4 Plasma-Assisted Annealing Process 204
9.3.4 Structure Modulation 205
9.3.4.1 Homojunction Dual-Active or Multiactive Layer 206
9.3.4.2 Heterojunction Dual- or Multiactive Layer 206
9.4 Applications of Flexible Electronics with Low-Temperature Solution-Processed Oxide TFTs 208
9.4.1 Flexible Displays 208
9.4.2 Flexible Sensors 208
9.4.3 Flexible Integrated Circuits 209
References 209
10 Recent Progress on Amorphous Oxide Semiconductor Thin-Film Transistors Using the Atomic Layer Deposition Technique 213
Hyun-Jun Jeong and Jin-Seong Park
10.1 Atomic Layer Deposition (ALD) for Amorphous Oxide Semiconductor (AOS) Applications 213
10.1.1 The ALD Technique 213
10.1.2 Research Motivation for ALD AOS Applications 215
10.2 AOS-TFTs Based on ALD 217
10.2.1 Binary Oxide Semiconductor TFTs Based on ALD 217
10.2.1.1 ZnO-TFTs 217
10.2.1.2 InOx-TFTs 218
10.2.1.3 SnOx-TFTs 218
10.2.2 Ternary and Quaternary Oxide Semiconductor TFTs Based on ALD 220
10.2.2.1 Indium-Zinc Oxide (IZO) and Indium-Gallium Oxide (IGO) 220
10.2.2.2 Zinc-Tin Oxide (ZTO) 223
10.2.2.3 Indium-Gallium-Zinc Oxide (IGZO) 223
10.2.2.4 Indium-Tin-Zinc Oxide (ITZO) 226
10.3 Challenging Issues of AOS Applications Using ALD 226
10.3.1 p-Type Oxide Semiconductors 226
10.3.1.1 Tin Monoxide (SnO) 228
10.3.1.2 Copper Oxide (cu x O) 229
10.3.2 Enhancing Device Performance: Mobility and Stability 230
10.3.2.1 Composition Gradient Oxide Semiconductors 230
10.3.2.2 Two-Dimensional Electron Gas (2DEG) Oxide Semiconductors 231
10.3.2.3 Spatial and Atmospheric ALD for Oxide Semiconductors 234
References 234
Part IV Thin-Film Transistors 239
11 Control of Carrier Concentrations in AOSs and Application to Bulk-Accumulation TFTs 241
Suhui Lee and Jin Jang
11.1 Introduction 241
11.2 Control of Carrier Concentration in a-IGZO 242
11.3 Effect of Carrier Concentration on the Performance of a-IGZO TFTs with a Dual-Gate Structure 247
11.3.1 Inverted Staggered TFTs 247
11.3.2 Coplanar TFTs 251
11.4 High-Drain-Current, Dual-Gate Oxide TFTs 252
11.5 Stability of Oxide TFTs: PBTS, NBIS, HCTS, Hysteresis, and Mechanical Strain 259
11.6 TFT Circuits: Ring Oscillators and Amplifier Circuits 266
11.7 Conclusion 270
References 270
12 Elevated-Metal Metal-Oxide Thin-Film Transistors: A Back-Gate Transistor Architecture with Annealing-Induced Source/Drain Regions 273
Man Wong, Zhihe Xia, and Jiapeng li
12.1 Introduction 273
12.1.1 Semiconducting Materials for a TFT 274
12.1.1.1 Amorphous Silicon 274
12.1.1.2 Low-Temperature Polycrystalline Silicon 274
12.1.1.3 MO Semiconductors 275
12.1.2 TFT Architectures 276
12.2 Annealing-Induced Generation of Donor Defects 279
12.2.1 Effects of Annealing on the Resistivity of IGZO 279
12.2.2 Microanalyses of the Thermally Annealed Samples 283
12.2.3 Lateral Migration of the Annealing-Induced Donor Defects 284
12.3 Elevated-Metal Metal-Oxide (EMMO) TFT Technology 286
12.3.1 Technology and Characteristics of IGZO EMMO TFTs 287
12.3.2 Applicability of EMMO Technology to Other MO Materials 291
12.3.3 Fluorinated EMMO TFTs 292
12.3.4 Resilience of Fluorinated MO against Hydrogen Doping 296
12.3.5 Technology and Display Resolution Trend 298
12.4 Enhanced EMMO TFT Technologies 301
12.4.1 3-EMMO TFT Technology 302
12.4.2 Self-Aligned EMMO TFTs 307
12.5 Conclusion 309
Acknowledgments 310
References 310
13 Hot Carrier Effects in Oxide-TFTs 315
Mami N. Fujii, Takanori Takahashi, Juan Paolo Soria Bermundo, and Yukiharu Uraoka
13.1 Introduction 315
13.2 Analysis of Hot Carrier Effect in IGZO-TFTs 315
13.2.1 Photoemission from IGZO-TFTs 315
13.2.2 Kink Current in Photon Emission Condition 318
13.2.3 Hot Carrier-Induced Degradation of a-IGZO-TFTs 318
13.3 Analysis of the Hot Carrier Effect in High-Mobility Oxide-TFTs 322
13.3.1 Bias Stability under DC Stresses in a High-Mobility IWZO-TFT 322
13.3.2 Analysis of Dynamic Stress in Oxide-TFTs 323
13.3.3 Photon Emission from the IWZO-TFT under Pulse Stress 323
13.4 Conclusion 328
References 328
14 Carbon-Related Impurities and NBS Instability in AOS-TFTs 333
Junghwan Kim and Hideo Hosono
14.1 Introduction 333
14.2 Experimental 334
14.3 Results and Discussion 334
14.4 Summary 337
References 339
Part V TFTs and Circuits 341
15 Oxide TFTs for Advanced Signal-Processing Architectures 343
Arokia Nathan, Denis Striakhilev, and Shuenn-Jiun Tang
15.1 Introduction 343
15.1.1 Device-Circuit Interactions 343
15.2 Above-Threshold TFT Operation and Defect Compensation: AMOLED Displays 345
15.2.1 AMOLED Display Challenges 345
15.2.2 Above-Threshold Operation 347
15.2.3 Temperature Dependence 347
15.2.4 Effects of Process-Induced Spatial Nonuniformity 349
15.2.5 Overview of External Compensation for AMOLED Displays 351
15.3 Ultralow-Power TFT Operation in a Deep Subthreshold (Near Off-State) Regime 354
15.3.1 Schottky Barrier TFTs 355
15.3.2 Device Characteristics and Small Signal Parameters 358
15.3.3 Common Source Amplifier 360
15.4 Oxide TFT-Based Image Sensors 362
15.4.1 Heterojunction Oxide Photo-TFTs 362
15.4.2 Persistent Photocurrent 364
15.4.3 All-Oxide Photosensor Array 365
References 366
16 Device Modeling and Simulation of TAOS-TFTs 369
Katsumi Abe
16.1 Introduction 369
16.2 Device Models for TAOS-TFTs 369
16.2.1 Mobility Model 369
16.2.2 Density of Subgap States (DOS) Model 371
16.2.3 Self-Heating Model 372
16.3 Applications 373
16.3.1 Temperature Dependence 373
16.3.2 Channel-Length Dependence 373
16.3.3 Channel-Width Dependence 375
16.3.4 Dual-Gate Structure 378
16.4 Reliability 379
16.5 Summary 381
Acknowledgments 381
References 382
17 Oxide Circuits for Flexible Electronics 383
Kris Myny, Nikolaos Papadopoulos, Florian De Roose, and Paul Heremans
17.1 Introduction 383
17.2 Technology-Aware Design Considerations 383
17.2.1 Etch-Stop Layer, Backchannel Etch, and Self-Aligned Transistors 384
17.2.1.1 Etch-Stop Layer 384
17.2.1.2 Backchannel Etch 385
17.2.1.3 Self-Aligned Transistors 385
17.2.1.4 Comparison 386
17.2.2 Dual-Gate Transistors 386
17.2.2.1 Stack Architecture 386
17.2.2.2 Effect of the Backgate 388
17.2.3 Moore's Law for TFT Technologies 389
17.2.3.1 Cmos 389
17.2.3.2 Thin-Film Electronics Historically 389
17.2.3.3 New Drivers for Thin-Film Scaling: Circuits 390
17.2.3.4 L-Scaling 391
17.2.3.5 W and L Scaling 391
17.2.3.6 Overall Lateral Scaling 391
17.2.3.7 Oxide Thickness and Supply Voltage Scaling 391
17.2.4 Conclusion 392
17.3 Digital Electronics 392
17.3.1 Communication Chips 392
17.3.2 Complex Metal-Oxide-Based Digital Chips 395
17.4 Analog Electronics 396
17.4.1 Thin-Film ADC Topologies 396
17.4.2 Imager Readout Peripherals 397
17.4.3 Healthcare Patches 399
17.5 Summary 400
Acknowledgments 400
References 400
Part VI Display and Memory Applications 405
18 Oxide TFT Technology for Printed Electronics 407
Toshiaki Arai
18.1 OLEDs 407
18.1.1 OLED Displays 407
18.1.2 Organic Light-Emitting Diodes 408
18.1.3 Printed OLEDs 409
18.2 TFTs for OLED Driving 413
18.2.1 TFT Candidates 413
18.2.2 Pixel Circuits 413
18.2.3 Oxide TFTs 414
18.2.3.1 Bottom-Gate TFTs 415
18.2.3.2 Top-Gate TFTs 418
18.3 Oxide TFT-Driven Printed OLED Displays 424
18.4 Summary 427
References 428
19 Mechanically Flexible Nonvolatile Memory Thin-Film Transistors Using Oxide Semiconductor Active Channels on Ultrathin Polyimide Films 431
Sung-Min Yoon, Hyeong-Rae Kim, Hye-Won Jang, Ji-Hee Yang, Hyo-Eun Kim, and Sol-Mi Kwak
19.1 Introduction 431
19.2 Fabrication of Memory TFTs 432
19.2.1 Substrate Preparation 432
19.2.2 Device Fabrication Procedures 434
19.2.3 Characterization Methodologies 435
19.3 Device Operations of Flexible Memory TFTs 437
19.3.1 Optimization of Flexible IGZO-TFTs on PI Films 437
19.3.2 Nonvolatile Memory Operations of Flexible Memory TFTs 438
19.3.3 Operation Mechanisms and Device Physics 442
19.4 Choice of Alternative Materials 444
19.4.1 Introduction to Conducting Polymer Electrodes 444
19.4.2 Introduction of Polymeric Gate Insulators 446
19.5 Device Scaling to Vertical-Channel Structures 447
19.5.1 Vertical-Channel IGZO-TFTs on PI Films 447
19.5.2 Vertical-Channel Memory TFTs Using IGZO Channel and ZnO Trap Layers 449
19.6 Summary 453
19.6.1 Remaining Technical Issues 453
19.6.2 Conclusions and Outlooks 453
References 454
20 Amorphous Oxide Semiconductor TFTs for BEOL Transistor Applications 457
Nobuyoshi Saito and Keiji Ikeda
20.1 Introduction 457
20.2 Improvement of Immunity to H 2 Annealing 458
20.3 Increase of Mobility and Reduction of S/D Parasitic Resistance 463
20.4 Demonstration of Extremely Low Off-State Leakage Current Characteristics 467
References 471
21 Ferroelectric-HfO 2 Transistor Memory with IGZO Channels 473
Masaharu Kobayashi
21.1 Introduction 473
21.2 Device Operation and Design 475
21.3 Device Fabrication 478
21.4 Experimental Results and Discussions 479
21.4.1 FE-HfO 2 Capacitors with an IGZO Layer 479
21.4.2 IGZO Channel FeFETs 481
21.5 Summary 484
Acknowledgments 484
References 485
22 Neuromorphic Chips Using AOS Thin-Film Devices 487
Mutsumi Kimura
22.1 Introduction 487
22.2 Neuromorphic Systems with Crosspoint-Type ?-GTO Thin-Film Devices 488
22.2.1 Neuromorphic Systems 488
22.2.1.1 ?-GTO Thin-Film Devices 488
22.2.1.2 System Architecture 489
22.2.2 Experimental Results 492
22.3 Neuromorphic System Using an LSI Chip and ?-IGZO Thin-Film Devices [24] 493
22.3.1 Neuromorphic System 494
22.3.1.1 Neuron Elements 494
22.3.1.2 Synapse Elements 494
22.3.1.3 System Architecture 495
22.3.2 Working Principle 495
22.3.2.1 Cellular Neural Network 495
22.3.2.2 Tug-of-War Method 497
22.3.2.3 Modified Hebbian Learning 497
22.3.2.4 Majority-Rule Handling 498
22.3.3 Experimental Results 498
22.3.3.1 Raw Data 498
22.3.3.2 Associative Memory 499
22.4 Conclusion 499
Acknowledgments 500
References 500
23 Oxide TFTs and Their Application to X-Ray Imaging 503
Robert A. Street
23.1 Introduction 503
23.2 Digital X-Ray Detection and Imaging Modalities 504
23.2.1 Indirect Detection Imaging 504
23.2.2 Direct Detection Imaging 505
23.2.3 X-Ray Imaging Modalities 505
23.3 Oxide-TFT X-Ray Detectors 506
23.3.1 TFT Backplane Requirements for Digital X-Rays 506
23.3.2 An IGZO Detector Fabrication and Characterization 506
23.3.3 Other Reported Oxide X-Ray Detectors 509
23.4 How Oxide TFTs Can Improve Digital X-Ray Detectors 509
23.4.1 Noise and Image Quality in X-Ray Detectors 510
23.4.2 Minimizing Additive Electronic Noise with Oxides 510
23.4.3 Pixel Amplifier Backplanes 511
23.4.4 IGZO-TFT Noise 511
23.5 Radiation Hardness of Oxide TFTs 513
23.6 Oxide Direct Detector Materials 515
23.7 Summary 515
References 515
Part VII New Materials 519
24 Toward the Development of High-Performance p-Channel Oxide-TFTs and All-Oxide Complementary Circuits 521
Kenji Nomura
24.1 Introduction 521
24.2 Why Is High-Performance p-Channel Oxide Difficult? 521
24.3 The Current Development of p-Channel Oxide-TFTs 524
24.4 Comparisons of p-Type Cu 2 O and SnO Channels 526
24.5 Comparisons of the TFT Characteristics of Cu 2 O and SnO-TFTs 529
24.6 Subgap Defect Termination for p-Channel Oxides 532
24.7 All-Oxide Complementary Circuits 534
24.8 Conclusions 535
References 536
25 Solution-Synthesized Metal Oxides and Halides for Transparent p-Channel TFTs 539
Ao Liu, Huihui Zhu, and Yong-Young Noh
25.1 Introduction 539
25.2 Solution-Processed p-Channel Metal-Oxide TFTs 540
25.3 Transparent Copper(I) Iodide (CuI)-Based TFTs 546
25.4 Conclusions and Perspectives 548
Acknowledgments 549
References 549
26 Tungsten-Doped Active Layers for High-Mobility AOS-TFTs 553
Zhang Qun
26.1 Introduction 553
26.2 Advances in Tungsten-Doped High-Mobility AOS-TFTs 555
26.2.1 a-IWO-TFTs 555
26.2.2 a-IZWO-TFTs 562
26.2.3 Dual Tungsten-Doped Active-Layer TFTs 565
26.2.4 Treatment on the Backchannel Surface 566
26.3 Perspectives for High-Mobility AOS Active Layers 570
References 572
27 Rare Earth- and Transition Metal-Doped Amorphous Oxide Semiconductor Phosphors for Novel Light-Emitting Diode Displays 577
Keisuke Ide, Junghwan Kim, Hideo Hosono, and Toshio Kamiya
27.1 Introduction 577
27.2 Eu-Doped Amorphous Oxide Semiconductor Phosphor 577
27.3 Multiple-Color Emissions from Various Rare Earth-Doped AOS Phosphors 579
27.4 Transition Metal-Doped AOS Phosphors 582
References 584
28 Application of AOSs to Charge Transport Layers in Electroluminescent Devices 585
Junghwan Kim and Hideo Hosono
28.1 Electronic Structure and Electrical Properties of Amorphous Oxide Semiconductors (AOSs) 585
28.2 Criteria for Charge Transport Layers in Electroluminescent (EL) Devices 585
28.3 Amorphous Zn-Si-O Electron Transport Layers for Perovskite Light-Emitting Diodes (PeLEDs) 587
28.4 Amorphous In-Mo-O Hole Injection Layers for OLEDs 589
28.5 Perspective 594
References 595
29 Displays and Vertical-Cavity Surface-Emitting Lasers 597
Kenichi Iga
29.1 Introduction to Displays 597
29.2 Liquid Crystal Displays (LCDs) 597
29.2.1 History of LCDs 597
29.2.2 Principle of LCD: The TN Mode 598
29.2.3 Other LC Modes 600
29.2.4 Light Sources 600
29.2.5 Diffusion Plate and Light Guiding Layer 601
29.2.6 Microlens Arrays 601
29.2.7 Short-Focal-Length Projection 602
29.3 Organic EL Display 602
29.3.1 Method (a): Color-Coding Method 603
29.3.2 Method (b): Filter Method 603
29.3.3 Method (c): Blue Conversion Method 603
29.4 Vertical-Cavity Surface-Emitting Lasers 604
29.4.1 Motivation of Invention 604
29.4.2 What Is the Difference? 605
29.4.3 Device Realization 605
29.4.4 Applications 607
29.5 Laser Displays including VCSELs 607
29.5.1 Laser Displays 607
29.5.2 Color Gamut 608
29.5.3 Laser Backlight Method 609
Acknowledgments 610
References 611
Index 613
Series Editor's Foreword xvii
About the Editors xviii
List of Contributors xix
Part I Introduction 1
1.1 Transparent Amorphous Oxide Semiconductors for Display Applications 3
Hideo Hosono
1.1.1 Introduction to Amorphous Semiconductors as Thin-Film Transistor (TFT) Channels 3
1.1.2 Historical Overview 4
1.1.3 Oxide and Silicon 6
1.1.4 Transparent Amorphous Oxide Semiconductors 6
1.1.4.1 Electronic Structures 6
1.1.4.2 Materials 8
1.1.4.3 Characteristic Carrier Transport Properties 9
1.1.4.4 Electronic States 10
1.1.5 P-Type Oxide Semiconductors for Display Applications 13
1.1.5.1 Oxides of Transition Metal Cations with an Electronic Configuration of (n?1)d 10 ns 0 (n = 4or5) 13
1.1.5.2 Oxides of Metal Cations with an Electronic Configuration of ns 2 13
1.1.5.3 Oxides of Metal Cations with an Electronic Configuration of nd 6 14
1.1.6 Novel Amorphous Oxide Semiconductors 15
1.1.7 Summary and Outlook 17
References 18
1.2 Transparent Amorphous Oxide Semiconductors 21
Hideya Kumomi
1.2.1 Introduction 21
1.2.2 Technical Issues and Requirements of TFTs for AM-FPDs 21
1.2.2.1 Field-Effect Mobility 21
1.2.2.2 Off-State Leakage Current and On/Off Current Ratio 23
1.2.2.3 Stability and Reliability 23
1.2.2.4 Uniformity 23
1.2.2.5 Large-Area Devices by Large-Area Mother-Glass Substrates 24
1.2.2.6 Low-Temperature Fabrication and Flexibility 24
1.2.3 History, Features, Uniqueness, Development, and Applications of AOS-TFTs 24
1.2.3.1 History 24
1.2.3.2 Features and Uniqueness 25
1.2.3.3 Applications 27
1.2.3.4 Development and Products of AM-FPDs 28
1.2.4 Summary 29
References 30
Part II Fundamentals 31
2 Electronic Structure and Structural Randomness 33
Julia E. Medvedeva, Bishal Bhattarai, and D. Bruce Buchholz
2.1 Introduction 33
2.2 Brief Description of Methods and Approaches 35
2.2.1 Computational Approach 35
2.2.2 Experimental Approach 36
2.3 The Structure and Properties of Crystalline and Amorphous In 2 O 3 36
2.4 The Structure and Properties of Crystalline and Amorphous SnO 2 43
2.5 The Structure and Properties of Crystalline and Amorphous ZnO 46
2.6 The Structure and Properties of Crystalline and Amorphous Ga 2 O 3 52
2.7 Role of Morphology in Structure-Property Relationships 57
2.8 The Role of Composition in Structure-Property Relationships: IGO and IGZO 64
2.9 Conclusions 69
References 70
3 Electronic Structure of Transparent Amorphous Oxide Semiconductors 73
John Robertson and Zhaofu Zhang
3.1 Introduction 73
3.2 Mobility 73
3.3 Density of States 74
3.4 Band Structures of n-Type Semiconductors 78
3.5 Instabilities 81
3.6 Doping Limits and Finding Effective Oxide Semiconductors 86
3.7 OLED Electrodes 88
3.8 Summary 89
References 89
4 Defects and Relevant Properties 93
Toshio Kamiya, Kenji Nomura, Keisuke Ide, and Hideo Hosono
4.1 Introduction 93
4.2 Typical Deposition Condition 93
4.3 Overview of Electronic Defects in AOSs 94
4.4 Origins of Electron Donors 96
4.5 Oxygen- and Hydrogen-Related Defects and Near-VBM States 98
4.6 Summary 102
References 102
5 Amorphous Semiconductor Mobility Physics and TFT Modeling 105
John F. Wager
5.1 Amorphous Semiconductor Mobility: An Introduction 105
5.2 Diffusive Mobility 106
5.3 Density of States 110
5.4 TFT Mobility Considerations 111
5.5 TFT Mobility Extraction, Fitting, and Model Validation 112
5.6 Physics-Based TFT Mobility Modeling 118
5.7 Conclusions 121
References 122
6 Percolation Description of Charge Transport in Amorphous Oxide Semiconductors: Band Conduction Dominated by Disorder 125
A. V. Nenashev, F. Gebhard, K. Meerholz, and S. D. Baranovskii
6.1 Introduction 125
6.2 Band Transport via Extended States in the Random-Barrier Model (RBM) 126
6.2.1 Deficiencies of the Rate-Averaging Approach: Electrotechnical Analogy 127
6.2.2 Percolation Approach to Charge Transport in the RBM 129
6.3 Random Band-Edge Model (RBEM) for Charge Transport in AOSs 131
6.4 Percolation Theory for Charge Transport in the RBEM 133
6.4.1 From Regional to Global Conductivities in Continuum Percolation Theory 133
6.4.2 Averaging Procedure by Adler et al. 135
6.5 Comparison between Percolation Theory and EMA 136
6.6 Comparison with Experimental Data 137
6.7 Discussion and Conclusions 140
6.7.1 Textbook Description of Charge Transport in Traditional Crystalline Semiconductors (TCSs) 140
6.7.2 Results of This Chapter for Charge Transport in Amorphous Oxide Semiconductors (AOSs) 141
Acknowledgments 141
References 141
7 State and Role of Hydrogen in Amorphous Oxide Semiconductors 145
Hideo Hosono and Toshio Kamiya
7.1 Introduction 145
7.2 Concentration and Chemical States 145
7.3 Carrier Generation and Hydrogen 150
7.3.1 Carrier Generation by H Injection at Low Temperatures 150
7.3.2 Carrier Generation and Annihilation by Thermal Treatment 151
7.4 Energy Levels and Electrical Properties 153
7.5 Incorporation and Conversion of H Impurities 154
7.6 Concluding Remarks 155
Acknowledgments 156
References 156
Part III Processing 159
8 Low-Temperature Thin-Film Combustion Synthesis of Metal-Oxide Semiconductors: Science and Technology 161
Binghao Wang, Wei Huang, Antonio Facchetti, and Tobin J. Marks
8.1 Introduction 161
8.2 Low-Temperature Solution-Processing Methodologies 162
8.2.1 Alkoxide Precursors 162
8.2.2 Microwave-Assisted Annealing 165
8.2.3 High-Pressure Annealing 165
8.2.4 Photonic Annealing 165
8.2.4.1 Laser Annealing 166
8.2.4.2 Deep-Ultraviolet Illumination 168
8.2.4.3 Flash Lamp Annealing 170
8.2.5 Redox Reactions 170
8.3 Combustion Synthesis for MO TFTs 171
8.3.1 n-Type MO TFTs 172
8.3.2 p-Type MO TFTs 178
8.4 Summary and Perspectives 180
Acknowledgments 180
References 181
9 Solution-Processed Metal-Oxide Thin-Film Transistors for Flexible Electronics 185
Hyun Jae Kim
9.1 Introduction 185
9.2 Fundamentals of Solution-Processed Metal-Oxide Thin-Film Transistors 187
9.2.1 Deposition Methods for Solution-Processed Oxide Semiconductors 187
9.2.1.1 Coating-Based Deposition Methods 190
9.2.1.2 Printing-Based Deposition Methods 191
9.2.2 The Formation Mechanism of Solution-Processed Oxide Semiconductor Films 194
9.3 Low-Temperature Technologies for Active-Layer Engineering of Solution-Processed Oxide TFTs 196
9.3.1 Overview 196
9.3.2 Solution Modulation 197
9.3.2.1 Alkoxide Precursors 198
9.3.2.2 pH Adjustment 199
9.3.2.3 Combustion Reactions 199
9.3.2.4 Aqueous Solvent 199
9.3.3 Process Modulation 201
9.3.3.1 Photoactivation Process 201
9.3.3.2 High-Pressure Annealing (HPA) Process 202
9.3.3.3 Microwave-Assisted Annealing Process 204
9.3.3.4 Plasma-Assisted Annealing Process 204
9.3.4 Structure Modulation 205
9.3.4.1 Homojunction Dual-Active or Multiactive Layer 206
9.3.4.2 Heterojunction Dual- or Multiactive Layer 206
9.4 Applications of Flexible Electronics with Low-Temperature Solution-Processed Oxide TFTs 208
9.4.1 Flexible Displays 208
9.4.2 Flexible Sensors 208
9.4.3 Flexible Integrated Circuits 209
References 209
10 Recent Progress on Amorphous Oxide Semiconductor Thin-Film Transistors Using the Atomic Layer Deposition Technique 213
Hyun-Jun Jeong and Jin-Seong Park
10.1 Atomic Layer Deposition (ALD) for Amorphous Oxide Semiconductor (AOS) Applications 213
10.1.1 The ALD Technique 213
10.1.2 Research Motivation for ALD AOS Applications 215
10.2 AOS-TFTs Based on ALD 217
10.2.1 Binary Oxide Semiconductor TFTs Based on ALD 217
10.2.1.1 ZnO-TFTs 217
10.2.1.2 InOx-TFTs 218
10.2.1.3 SnOx-TFTs 218
10.2.2 Ternary and Quaternary Oxide Semiconductor TFTs Based on ALD 220
10.2.2.1 Indium-Zinc Oxide (IZO) and Indium-Gallium Oxide (IGO) 220
10.2.2.2 Zinc-Tin Oxide (ZTO) 223
10.2.2.3 Indium-Gallium-Zinc Oxide (IGZO) 223
10.2.2.4 Indium-Tin-Zinc Oxide (ITZO) 226
10.3 Challenging Issues of AOS Applications Using ALD 226
10.3.1 p-Type Oxide Semiconductors 226
10.3.1.1 Tin Monoxide (SnO) 228
10.3.1.2 Copper Oxide (cu x O) 229
10.3.2 Enhancing Device Performance: Mobility and Stability 230
10.3.2.1 Composition Gradient Oxide Semiconductors 230
10.3.2.2 Two-Dimensional Electron Gas (2DEG) Oxide Semiconductors 231
10.3.2.3 Spatial and Atmospheric ALD for Oxide Semiconductors 234
References 234
Part IV Thin-Film Transistors 239
11 Control of Carrier Concentrations in AOSs and Application to Bulk-Accumulation TFTs 241
Suhui Lee and Jin Jang
11.1 Introduction 241
11.2 Control of Carrier Concentration in a-IGZO 242
11.3 Effect of Carrier Concentration on the Performance of a-IGZO TFTs with a Dual-Gate Structure 247
11.3.1 Inverted Staggered TFTs 247
11.3.2 Coplanar TFTs 251
11.4 High-Drain-Current, Dual-Gate Oxide TFTs 252
11.5 Stability of Oxide TFTs: PBTS, NBIS, HCTS, Hysteresis, and Mechanical Strain 259
11.6 TFT Circuits: Ring Oscillators and Amplifier Circuits 266
11.7 Conclusion 270
References 270
12 Elevated-Metal Metal-Oxide Thin-Film Transistors: A Back-Gate Transistor Architecture with Annealing-Induced Source/Drain Regions 273
Man Wong, Zhihe Xia, and Jiapeng li
12.1 Introduction 273
12.1.1 Semiconducting Materials for a TFT 274
12.1.1.1 Amorphous Silicon 274
12.1.1.2 Low-Temperature Polycrystalline Silicon 274
12.1.1.3 MO Semiconductors 275
12.1.2 TFT Architectures 276
12.2 Annealing-Induced Generation of Donor Defects 279
12.2.1 Effects of Annealing on the Resistivity of IGZO 279
12.2.2 Microanalyses of the Thermally Annealed Samples 283
12.2.3 Lateral Migration of the Annealing-Induced Donor Defects 284
12.3 Elevated-Metal Metal-Oxide (EMMO) TFT Technology 286
12.3.1 Technology and Characteristics of IGZO EMMO TFTs 287
12.3.2 Applicability of EMMO Technology to Other MO Materials 291
12.3.3 Fluorinated EMMO TFTs 292
12.3.4 Resilience of Fluorinated MO against Hydrogen Doping 296
12.3.5 Technology and Display Resolution Trend 298
12.4 Enhanced EMMO TFT Technologies 301
12.4.1 3-EMMO TFT Technology 302
12.4.2 Self-Aligned EMMO TFTs 307
12.5 Conclusion 309
Acknowledgments 310
References 310
13 Hot Carrier Effects in Oxide-TFTs 315
Mami N. Fujii, Takanori Takahashi, Juan Paolo Soria Bermundo, and Yukiharu Uraoka
13.1 Introduction 315
13.2 Analysis of Hot Carrier Effect in IGZO-TFTs 315
13.2.1 Photoemission from IGZO-TFTs 315
13.2.2 Kink Current in Photon Emission Condition 318
13.2.3 Hot Carrier-Induced Degradation of a-IGZO-TFTs 318
13.3 Analysis of the Hot Carrier Effect in High-Mobility Oxide-TFTs 322
13.3.1 Bias Stability under DC Stresses in a High-Mobility IWZO-TFT 322
13.3.2 Analysis of Dynamic Stress in Oxide-TFTs 323
13.3.3 Photon Emission from the IWZO-TFT under Pulse Stress 323
13.4 Conclusion 328
References 328
14 Carbon-Related Impurities and NBS Instability in AOS-TFTs 333
Junghwan Kim and Hideo Hosono
14.1 Introduction 333
14.2 Experimental 334
14.3 Results and Discussion 334
14.4 Summary 337
References 339
Part V TFTs and Circuits 341
15 Oxide TFTs for Advanced Signal-Processing Architectures 343
Arokia Nathan, Denis Striakhilev, and Shuenn-Jiun Tang
15.1 Introduction 343
15.1.1 Device-Circuit Interactions 343
15.2 Above-Threshold TFT Operation and Defect Compensation: AMOLED Displays 345
15.2.1 AMOLED Display Challenges 345
15.2.2 Above-Threshold Operation 347
15.2.3 Temperature Dependence 347
15.2.4 Effects of Process-Induced Spatial Nonuniformity 349
15.2.5 Overview of External Compensation for AMOLED Displays 351
15.3 Ultralow-Power TFT Operation in a Deep Subthreshold (Near Off-State) Regime 354
15.3.1 Schottky Barrier TFTs 355
15.3.2 Device Characteristics and Small Signal Parameters 358
15.3.3 Common Source Amplifier 360
15.4 Oxide TFT-Based Image Sensors 362
15.4.1 Heterojunction Oxide Photo-TFTs 362
15.4.2 Persistent Photocurrent 364
15.4.3 All-Oxide Photosensor Array 365
References 366
16 Device Modeling and Simulation of TAOS-TFTs 369
Katsumi Abe
16.1 Introduction 369
16.2 Device Models for TAOS-TFTs 369
16.2.1 Mobility Model 369
16.2.2 Density of Subgap States (DOS) Model 371
16.2.3 Self-Heating Model 372
16.3 Applications 373
16.3.1 Temperature Dependence 373
16.3.2 Channel-Length Dependence 373
16.3.3 Channel-Width Dependence 375
16.3.4 Dual-Gate Structure 378
16.4 Reliability 379
16.5 Summary 381
Acknowledgments 381
References 382
17 Oxide Circuits for Flexible Electronics 383
Kris Myny, Nikolaos Papadopoulos, Florian De Roose, and Paul Heremans
17.1 Introduction 383
17.2 Technology-Aware Design Considerations 383
17.2.1 Etch-Stop Layer, Backchannel Etch, and Self-Aligned Transistors 384
17.2.1.1 Etch-Stop Layer 384
17.2.1.2 Backchannel Etch 385
17.2.1.3 Self-Aligned Transistors 385
17.2.1.4 Comparison 386
17.2.2 Dual-Gate Transistors 386
17.2.2.1 Stack Architecture 386
17.2.2.2 Effect of the Backgate 388
17.2.3 Moore's Law for TFT Technologies 389
17.2.3.1 Cmos 389
17.2.3.2 Thin-Film Electronics Historically 389
17.2.3.3 New Drivers for Thin-Film Scaling: Circuits 390
17.2.3.4 L-Scaling 391
17.2.3.5 W and L Scaling 391
17.2.3.6 Overall Lateral Scaling 391
17.2.3.7 Oxide Thickness and Supply Voltage Scaling 391
17.2.4 Conclusion 392
17.3 Digital Electronics 392
17.3.1 Communication Chips 392
17.3.2 Complex Metal-Oxide-Based Digital Chips 395
17.4 Analog Electronics 396
17.4.1 Thin-Film ADC Topologies 396
17.4.2 Imager Readout Peripherals 397
17.4.3 Healthcare Patches 399
17.5 Summary 400
Acknowledgments 400
References 400
Part VI Display and Memory Applications 405
18 Oxide TFT Technology for Printed Electronics 407
Toshiaki Arai
18.1 OLEDs 407
18.1.1 OLED Displays 407
18.1.2 Organic Light-Emitting Diodes 408
18.1.3 Printed OLEDs 409
18.2 TFTs for OLED Driving 413
18.2.1 TFT Candidates 413
18.2.2 Pixel Circuits 413
18.2.3 Oxide TFTs 414
18.2.3.1 Bottom-Gate TFTs 415
18.2.3.2 Top-Gate TFTs 418
18.3 Oxide TFT-Driven Printed OLED Displays 424
18.4 Summary 427
References 428
19 Mechanically Flexible Nonvolatile Memory Thin-Film Transistors Using Oxide Semiconductor Active Channels on Ultrathin Polyimide Films 431
Sung-Min Yoon, Hyeong-Rae Kim, Hye-Won Jang, Ji-Hee Yang, Hyo-Eun Kim, and Sol-Mi Kwak
19.1 Introduction 431
19.2 Fabrication of Memory TFTs 432
19.2.1 Substrate Preparation 432
19.2.2 Device Fabrication Procedures 434
19.2.3 Characterization Methodologies 435
19.3 Device Operations of Flexible Memory TFTs 437
19.3.1 Optimization of Flexible IGZO-TFTs on PI Films 437
19.3.2 Nonvolatile Memory Operations of Flexible Memory TFTs 438
19.3.3 Operation Mechanisms and Device Physics 442
19.4 Choice of Alternative Materials 444
19.4.1 Introduction to Conducting Polymer Electrodes 444
19.4.2 Introduction of Polymeric Gate Insulators 446
19.5 Device Scaling to Vertical-Channel Structures 447
19.5.1 Vertical-Channel IGZO-TFTs on PI Films 447
19.5.2 Vertical-Channel Memory TFTs Using IGZO Channel and ZnO Trap Layers 449
19.6 Summary 453
19.6.1 Remaining Technical Issues 453
19.6.2 Conclusions and Outlooks 453
References 454
20 Amorphous Oxide Semiconductor TFTs for BEOL Transistor Applications 457
Nobuyoshi Saito and Keiji Ikeda
20.1 Introduction 457
20.2 Improvement of Immunity to H 2 Annealing 458
20.3 Increase of Mobility and Reduction of S/D Parasitic Resistance 463
20.4 Demonstration of Extremely Low Off-State Leakage Current Characteristics 467
References 471
21 Ferroelectric-HfO 2 Transistor Memory with IGZO Channels 473
Masaharu Kobayashi
21.1 Introduction 473
21.2 Device Operation and Design 475
21.3 Device Fabrication 478
21.4 Experimental Results and Discussions 479
21.4.1 FE-HfO 2 Capacitors with an IGZO Layer 479
21.4.2 IGZO Channel FeFETs 481
21.5 Summary 484
Acknowledgments 484
References 485
22 Neuromorphic Chips Using AOS Thin-Film Devices 487
Mutsumi Kimura
22.1 Introduction 487
22.2 Neuromorphic Systems with Crosspoint-Type ?-GTO Thin-Film Devices 488
22.2.1 Neuromorphic Systems 488
22.2.1.1 ?-GTO Thin-Film Devices 488
22.2.1.2 System Architecture 489
22.2.2 Experimental Results 492
22.3 Neuromorphic System Using an LSI Chip and ?-IGZO Thin-Film Devices [24] 493
22.3.1 Neuromorphic System 494
22.3.1.1 Neuron Elements 494
22.3.1.2 Synapse Elements 494
22.3.1.3 System Architecture 495
22.3.2 Working Principle 495
22.3.2.1 Cellular Neural Network 495
22.3.2.2 Tug-of-War Method 497
22.3.2.3 Modified Hebbian Learning 497
22.3.2.4 Majority-Rule Handling 498
22.3.3 Experimental Results 498
22.3.3.1 Raw Data 498
22.3.3.2 Associative Memory 499
22.4 Conclusion 499
Acknowledgments 500
References 500
23 Oxide TFTs and Their Application to X-Ray Imaging 503
Robert A. Street
23.1 Introduction 503
23.2 Digital X-Ray Detection and Imaging Modalities 504
23.2.1 Indirect Detection Imaging 504
23.2.2 Direct Detection Imaging 505
23.2.3 X-Ray Imaging Modalities 505
23.3 Oxide-TFT X-Ray Detectors 506
23.3.1 TFT Backplane Requirements for Digital X-Rays 506
23.3.2 An IGZO Detector Fabrication and Characterization 506
23.3.3 Other Reported Oxide X-Ray Detectors 509
23.4 How Oxide TFTs Can Improve Digital X-Ray Detectors 509
23.4.1 Noise and Image Quality in X-Ray Detectors 510
23.4.2 Minimizing Additive Electronic Noise with Oxides 510
23.4.3 Pixel Amplifier Backplanes 511
23.4.4 IGZO-TFT Noise 511
23.5 Radiation Hardness of Oxide TFTs 513
23.6 Oxide Direct Detector Materials 515
23.7 Summary 515
References 515
Part VII New Materials 519
24 Toward the Development of High-Performance p-Channel Oxide-TFTs and All-Oxide Complementary Circuits 521
Kenji Nomura
24.1 Introduction 521
24.2 Why Is High-Performance p-Channel Oxide Difficult? 521
24.3 The Current Development of p-Channel Oxide-TFTs 524
24.4 Comparisons of p-Type Cu 2 O and SnO Channels 526
24.5 Comparisons of the TFT Characteristics of Cu 2 O and SnO-TFTs 529
24.6 Subgap Defect Termination for p-Channel Oxides 532
24.7 All-Oxide Complementary Circuits 534
24.8 Conclusions 535
References 536
25 Solution-Synthesized Metal Oxides and Halides for Transparent p-Channel TFTs 539
Ao Liu, Huihui Zhu, and Yong-Young Noh
25.1 Introduction 539
25.2 Solution-Processed p-Channel Metal-Oxide TFTs 540
25.3 Transparent Copper(I) Iodide (CuI)-Based TFTs 546
25.4 Conclusions and Perspectives 548
Acknowledgments 549
References 549
26 Tungsten-Doped Active Layers for High-Mobility AOS-TFTs 553
Zhang Qun
26.1 Introduction 553
26.2 Advances in Tungsten-Doped High-Mobility AOS-TFTs 555
26.2.1 a-IWO-TFTs 555
26.2.2 a-IZWO-TFTs 562
26.2.3 Dual Tungsten-Doped Active-Layer TFTs 565
26.2.4 Treatment on the Backchannel Surface 566
26.3 Perspectives for High-Mobility AOS Active Layers 570
References 572
27 Rare Earth- and Transition Metal-Doped Amorphous Oxide Semiconductor Phosphors for Novel Light-Emitting Diode Displays 577
Keisuke Ide, Junghwan Kim, Hideo Hosono, and Toshio Kamiya
27.1 Introduction 577
27.2 Eu-Doped Amorphous Oxide Semiconductor Phosphor 577
27.3 Multiple-Color Emissions from Various Rare Earth-Doped AOS Phosphors 579
27.4 Transition Metal-Doped AOS Phosphors 582
References 584
28 Application of AOSs to Charge Transport Layers in Electroluminescent Devices 585
Junghwan Kim and Hideo Hosono
28.1 Electronic Structure and Electrical Properties of Amorphous Oxide Semiconductors (AOSs) 585
28.2 Criteria for Charge Transport Layers in Electroluminescent (EL) Devices 585
28.3 Amorphous Zn-Si-O Electron Transport Layers for Perovskite Light-Emitting Diodes (PeLEDs) 587
28.4 Amorphous In-Mo-O Hole Injection Layers for OLEDs 589
28.5 Perspective 594
References 595
29 Displays and Vertical-Cavity Surface-Emitting Lasers 597
Kenichi Iga
29.1 Introduction to Displays 597
29.2 Liquid Crystal Displays (LCDs) 597
29.2.1 History of LCDs 597
29.2.2 Principle of LCD: The TN Mode 598
29.2.3 Other LC Modes 600
29.2.4 Light Sources 600
29.2.5 Diffusion Plate and Light Guiding Layer 601
29.2.6 Microlens Arrays 601
29.2.7 Short-Focal-Length Projection 602
29.3 Organic EL Display 602
29.3.1 Method (a): Color-Coding Method 603
29.3.2 Method (b): Filter Method 603
29.3.3 Method (c): Blue Conversion Method 603
29.4 Vertical-Cavity Surface-Emitting Lasers 604
29.4.1 Motivation of Invention 604
29.4.2 What Is the Difference? 605
29.4.3 Device Realization 605
29.4.4 Applications 607
29.5 Laser Displays including VCSELs 607
29.5.1 Laser Displays 607
29.5.2 Color Gamut 608
29.5.3 Laser Backlight Method 609
Acknowledgments 610
References 611
Index 613
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Transparent semiconductors; thin film transistors; tft; flexible semiconductors; high mobility semiconductors; amorphous oxide semiconductor textbook; amorphous oxide semiconductor guide; amorphous oxide semiconductor research; materials design
Preface xv
Series Editor's Foreword xvii
About the Editors xviii
List of Contributors xix
Part I Introduction 1
1.1 Transparent Amorphous Oxide Semiconductors for Display Applications 3
Hideo Hosono
1.1.1 Introduction to Amorphous Semiconductors as Thin-Film Transistor (TFT) Channels 3
1.1.2 Historical Overview 4
1.1.3 Oxide and Silicon 6
1.1.4 Transparent Amorphous Oxide Semiconductors 6
1.1.4.1 Electronic Structures 6
1.1.4.2 Materials 8
1.1.4.3 Characteristic Carrier Transport Properties 9
1.1.4.4 Electronic States 10
1.1.5 P-Type Oxide Semiconductors for Display Applications 13
1.1.5.1 Oxides of Transition Metal Cations with an Electronic Configuration of (n?1)d 10 ns 0 (n = 4or5) 13
1.1.5.2 Oxides of Metal Cations with an Electronic Configuration of ns 2 13
1.1.5.3 Oxides of Metal Cations with an Electronic Configuration of nd 6 14
1.1.6 Novel Amorphous Oxide Semiconductors 15
1.1.7 Summary and Outlook 17
References 18
1.2 Transparent Amorphous Oxide Semiconductors 21
Hideya Kumomi
1.2.1 Introduction 21
1.2.2 Technical Issues and Requirements of TFTs for AM-FPDs 21
1.2.2.1 Field-Effect Mobility 21
1.2.2.2 Off-State Leakage Current and On/Off Current Ratio 23
1.2.2.3 Stability and Reliability 23
1.2.2.4 Uniformity 23
1.2.2.5 Large-Area Devices by Large-Area Mother-Glass Substrates 24
1.2.2.6 Low-Temperature Fabrication and Flexibility 24
1.2.3 History, Features, Uniqueness, Development, and Applications of AOS-TFTs 24
1.2.3.1 History 24
1.2.3.2 Features and Uniqueness 25
1.2.3.3 Applications 27
1.2.3.4 Development and Products of AM-FPDs 28
1.2.4 Summary 29
References 30
Part II Fundamentals 31
2 Electronic Structure and Structural Randomness 33
Julia E. Medvedeva, Bishal Bhattarai, and D. Bruce Buchholz
2.1 Introduction 33
2.2 Brief Description of Methods and Approaches 35
2.2.1 Computational Approach 35
2.2.2 Experimental Approach 36
2.3 The Structure and Properties of Crystalline and Amorphous In 2 O 3 36
2.4 The Structure and Properties of Crystalline and Amorphous SnO 2 43
2.5 The Structure and Properties of Crystalline and Amorphous ZnO 46
2.6 The Structure and Properties of Crystalline and Amorphous Ga 2 O 3 52
2.7 Role of Morphology in Structure-Property Relationships 57
2.8 The Role of Composition in Structure-Property Relationships: IGO and IGZO 64
2.9 Conclusions 69
References 70
3 Electronic Structure of Transparent Amorphous Oxide Semiconductors 73
John Robertson and Zhaofu Zhang
3.1 Introduction 73
3.2 Mobility 73
3.3 Density of States 74
3.4 Band Structures of n-Type Semiconductors 78
3.5 Instabilities 81
3.6 Doping Limits and Finding Effective Oxide Semiconductors 86
3.7 OLED Electrodes 88
3.8 Summary 89
References 89
4 Defects and Relevant Properties 93
Toshio Kamiya, Kenji Nomura, Keisuke Ide, and Hideo Hosono
4.1 Introduction 93
4.2 Typical Deposition Condition 93
4.3 Overview of Electronic Defects in AOSs 94
4.4 Origins of Electron Donors 96
4.5 Oxygen- and Hydrogen-Related Defects and Near-VBM States 98
4.6 Summary 102
References 102
5 Amorphous Semiconductor Mobility Physics and TFT Modeling 105
John F. Wager
5.1 Amorphous Semiconductor Mobility: An Introduction 105
5.2 Diffusive Mobility 106
5.3 Density of States 110
5.4 TFT Mobility Considerations 111
5.5 TFT Mobility Extraction, Fitting, and Model Validation 112
5.6 Physics-Based TFT Mobility Modeling 118
5.7 Conclusions 121
References 122
6 Percolation Description of Charge Transport in Amorphous Oxide Semiconductors: Band Conduction Dominated by Disorder 125
A. V. Nenashev, F. Gebhard, K. Meerholz, and S. D. Baranovskii
6.1 Introduction 125
6.2 Band Transport via Extended States in the Random-Barrier Model (RBM) 126
6.2.1 Deficiencies of the Rate-Averaging Approach: Electrotechnical Analogy 127
6.2.2 Percolation Approach to Charge Transport in the RBM 129
6.3 Random Band-Edge Model (RBEM) for Charge Transport in AOSs 131
6.4 Percolation Theory for Charge Transport in the RBEM 133
6.4.1 From Regional to Global Conductivities in Continuum Percolation Theory 133
6.4.2 Averaging Procedure by Adler et al. 135
6.5 Comparison between Percolation Theory and EMA 136
6.6 Comparison with Experimental Data 137
6.7 Discussion and Conclusions 140
6.7.1 Textbook Description of Charge Transport in Traditional Crystalline Semiconductors (TCSs) 140
6.7.2 Results of This Chapter for Charge Transport in Amorphous Oxide Semiconductors (AOSs) 141
Acknowledgments 141
References 141
7 State and Role of Hydrogen in Amorphous Oxide Semiconductors 145
Hideo Hosono and Toshio Kamiya
7.1 Introduction 145
7.2 Concentration and Chemical States 145
7.3 Carrier Generation and Hydrogen 150
7.3.1 Carrier Generation by H Injection at Low Temperatures 150
7.3.2 Carrier Generation and Annihilation by Thermal Treatment 151
7.4 Energy Levels and Electrical Properties 153
7.5 Incorporation and Conversion of H Impurities 154
7.6 Concluding Remarks 155
Acknowledgments 156
References 156
Part III Processing 159
8 Low-Temperature Thin-Film Combustion Synthesis of Metal-Oxide Semiconductors: Science and Technology 161
Binghao Wang, Wei Huang, Antonio Facchetti, and Tobin J. Marks
8.1 Introduction 161
8.2 Low-Temperature Solution-Processing Methodologies 162
8.2.1 Alkoxide Precursors 162
8.2.2 Microwave-Assisted Annealing 165
8.2.3 High-Pressure Annealing 165
8.2.4 Photonic Annealing 165
8.2.4.1 Laser Annealing 166
8.2.4.2 Deep-Ultraviolet Illumination 168
8.2.4.3 Flash Lamp Annealing 170
8.2.5 Redox Reactions 170
8.3 Combustion Synthesis for MO TFTs 171
8.3.1 n-Type MO TFTs 172
8.3.2 p-Type MO TFTs 178
8.4 Summary and Perspectives 180
Acknowledgments 180
References 181
9 Solution-Processed Metal-Oxide Thin-Film Transistors for Flexible Electronics 185
Hyun Jae Kim
9.1 Introduction 185
9.2 Fundamentals of Solution-Processed Metal-Oxide Thin-Film Transistors 187
9.2.1 Deposition Methods for Solution-Processed Oxide Semiconductors 187
9.2.1.1 Coating-Based Deposition Methods 190
9.2.1.2 Printing-Based Deposition Methods 191
9.2.2 The Formation Mechanism of Solution-Processed Oxide Semiconductor Films 194
9.3 Low-Temperature Technologies for Active-Layer Engineering of Solution-Processed Oxide TFTs 196
9.3.1 Overview 196
9.3.2 Solution Modulation 197
9.3.2.1 Alkoxide Precursors 198
9.3.2.2 pH Adjustment 199
9.3.2.3 Combustion Reactions 199
9.3.2.4 Aqueous Solvent 199
9.3.3 Process Modulation 201
9.3.3.1 Photoactivation Process 201
9.3.3.2 High-Pressure Annealing (HPA) Process 202
9.3.3.3 Microwave-Assisted Annealing Process 204
9.3.3.4 Plasma-Assisted Annealing Process 204
9.3.4 Structure Modulation 205
9.3.4.1 Homojunction Dual-Active or Multiactive Layer 206
9.3.4.2 Heterojunction Dual- or Multiactive Layer 206
9.4 Applications of Flexible Electronics with Low-Temperature Solution-Processed Oxide TFTs 208
9.4.1 Flexible Displays 208
9.4.2 Flexible Sensors 208
9.4.3 Flexible Integrated Circuits 209
References 209
10 Recent Progress on Amorphous Oxide Semiconductor Thin-Film Transistors Using the Atomic Layer Deposition Technique 213
Hyun-Jun Jeong and Jin-Seong Park
10.1 Atomic Layer Deposition (ALD) for Amorphous Oxide Semiconductor (AOS) Applications 213
10.1.1 The ALD Technique 213
10.1.2 Research Motivation for ALD AOS Applications 215
10.2 AOS-TFTs Based on ALD 217
10.2.1 Binary Oxide Semiconductor TFTs Based on ALD 217
10.2.1.1 ZnO-TFTs 217
10.2.1.2 InOx-TFTs 218
10.2.1.3 SnOx-TFTs 218
10.2.2 Ternary and Quaternary Oxide Semiconductor TFTs Based on ALD 220
10.2.2.1 Indium-Zinc Oxide (IZO) and Indium-Gallium Oxide (IGO) 220
10.2.2.2 Zinc-Tin Oxide (ZTO) 223
10.2.2.3 Indium-Gallium-Zinc Oxide (IGZO) 223
10.2.2.4 Indium-Tin-Zinc Oxide (ITZO) 226
10.3 Challenging Issues of AOS Applications Using ALD 226
10.3.1 p-Type Oxide Semiconductors 226
10.3.1.1 Tin Monoxide (SnO) 228
10.3.1.2 Copper Oxide (cu x O) 229
10.3.2 Enhancing Device Performance: Mobility and Stability 230
10.3.2.1 Composition Gradient Oxide Semiconductors 230
10.3.2.2 Two-Dimensional Electron Gas (2DEG) Oxide Semiconductors 231
10.3.2.3 Spatial and Atmospheric ALD for Oxide Semiconductors 234
References 234
Part IV Thin-Film Transistors 239
11 Control of Carrier Concentrations in AOSs and Application to Bulk-Accumulation TFTs 241
Suhui Lee and Jin Jang
11.1 Introduction 241
11.2 Control of Carrier Concentration in a-IGZO 242
11.3 Effect of Carrier Concentration on the Performance of a-IGZO TFTs with a Dual-Gate Structure 247
11.3.1 Inverted Staggered TFTs 247
11.3.2 Coplanar TFTs 251
11.4 High-Drain-Current, Dual-Gate Oxide TFTs 252
11.5 Stability of Oxide TFTs: PBTS, NBIS, HCTS, Hysteresis, and Mechanical Strain 259
11.6 TFT Circuits: Ring Oscillators and Amplifier Circuits 266
11.7 Conclusion 270
References 270
12 Elevated-Metal Metal-Oxide Thin-Film Transistors: A Back-Gate Transistor Architecture with Annealing-Induced Source/Drain Regions 273
Man Wong, Zhihe Xia, and Jiapeng li
12.1 Introduction 273
12.1.1 Semiconducting Materials for a TFT 274
12.1.1.1 Amorphous Silicon 274
12.1.1.2 Low-Temperature Polycrystalline Silicon 274
12.1.1.3 MO Semiconductors 275
12.1.2 TFT Architectures 276
12.2 Annealing-Induced Generation of Donor Defects 279
12.2.1 Effects of Annealing on the Resistivity of IGZO 279
12.2.2 Microanalyses of the Thermally Annealed Samples 283
12.2.3 Lateral Migration of the Annealing-Induced Donor Defects 284
12.3 Elevated-Metal Metal-Oxide (EMMO) TFT Technology 286
12.3.1 Technology and Characteristics of IGZO EMMO TFTs 287
12.3.2 Applicability of EMMO Technology to Other MO Materials 291
12.3.3 Fluorinated EMMO TFTs 292
12.3.4 Resilience of Fluorinated MO against Hydrogen Doping 296
12.3.5 Technology and Display Resolution Trend 298
12.4 Enhanced EMMO TFT Technologies 301
12.4.1 3-EMMO TFT Technology 302
12.4.2 Self-Aligned EMMO TFTs 307
12.5 Conclusion 309
Acknowledgments 310
References 310
13 Hot Carrier Effects in Oxide-TFTs 315
Mami N. Fujii, Takanori Takahashi, Juan Paolo Soria Bermundo, and Yukiharu Uraoka
13.1 Introduction 315
13.2 Analysis of Hot Carrier Effect in IGZO-TFTs 315
13.2.1 Photoemission from IGZO-TFTs 315
13.2.2 Kink Current in Photon Emission Condition 318
13.2.3 Hot Carrier-Induced Degradation of a-IGZO-TFTs 318
13.3 Analysis of the Hot Carrier Effect in High-Mobility Oxide-TFTs 322
13.3.1 Bias Stability under DC Stresses in a High-Mobility IWZO-TFT 322
13.3.2 Analysis of Dynamic Stress in Oxide-TFTs 323
13.3.3 Photon Emission from the IWZO-TFT under Pulse Stress 323
13.4 Conclusion 328
References 328
14 Carbon-Related Impurities and NBS Instability in AOS-TFTs 333
Junghwan Kim and Hideo Hosono
14.1 Introduction 333
14.2 Experimental 334
14.3 Results and Discussion 334
14.4 Summary 337
References 339
Part V TFTs and Circuits 341
15 Oxide TFTs for Advanced Signal-Processing Architectures 343
Arokia Nathan, Denis Striakhilev, and Shuenn-Jiun Tang
15.1 Introduction 343
15.1.1 Device-Circuit Interactions 343
15.2 Above-Threshold TFT Operation and Defect Compensation: AMOLED Displays 345
15.2.1 AMOLED Display Challenges 345
15.2.2 Above-Threshold Operation 347
15.2.3 Temperature Dependence 347
15.2.4 Effects of Process-Induced Spatial Nonuniformity 349
15.2.5 Overview of External Compensation for AMOLED Displays 351
15.3 Ultralow-Power TFT Operation in a Deep Subthreshold (Near Off-State) Regime 354
15.3.1 Schottky Barrier TFTs 355
15.3.2 Device Characteristics and Small Signal Parameters 358
15.3.3 Common Source Amplifier 360
15.4 Oxide TFT-Based Image Sensors 362
15.4.1 Heterojunction Oxide Photo-TFTs 362
15.4.2 Persistent Photocurrent 364
15.4.3 All-Oxide Photosensor Array 365
References 366
16 Device Modeling and Simulation of TAOS-TFTs 369
Katsumi Abe
16.1 Introduction 369
16.2 Device Models for TAOS-TFTs 369
16.2.1 Mobility Model 369
16.2.2 Density of Subgap States (DOS) Model 371
16.2.3 Self-Heating Model 372
16.3 Applications 373
16.3.1 Temperature Dependence 373
16.3.2 Channel-Length Dependence 373
16.3.3 Channel-Width Dependence 375
16.3.4 Dual-Gate Structure 378
16.4 Reliability 379
16.5 Summary 381
Acknowledgments 381
References 382
17 Oxide Circuits for Flexible Electronics 383
Kris Myny, Nikolaos Papadopoulos, Florian De Roose, and Paul Heremans
17.1 Introduction 383
17.2 Technology-Aware Design Considerations 383
17.2.1 Etch-Stop Layer, Backchannel Etch, and Self-Aligned Transistors 384
17.2.1.1 Etch-Stop Layer 384
17.2.1.2 Backchannel Etch 385
17.2.1.3 Self-Aligned Transistors 385
17.2.1.4 Comparison 386
17.2.2 Dual-Gate Transistors 386
17.2.2.1 Stack Architecture 386
17.2.2.2 Effect of the Backgate 388
17.2.3 Moore's Law for TFT Technologies 389
17.2.3.1 Cmos 389
17.2.3.2 Thin-Film Electronics Historically 389
17.2.3.3 New Drivers for Thin-Film Scaling: Circuits 390
17.2.3.4 L-Scaling 391
17.2.3.5 W and L Scaling 391
17.2.3.6 Overall Lateral Scaling 391
17.2.3.7 Oxide Thickness and Supply Voltage Scaling 391
17.2.4 Conclusion 392
17.3 Digital Electronics 392
17.3.1 Communication Chips 392
17.3.2 Complex Metal-Oxide-Based Digital Chips 395
17.4 Analog Electronics 396
17.4.1 Thin-Film ADC Topologies 396
17.4.2 Imager Readout Peripherals 397
17.4.3 Healthcare Patches 399
17.5 Summary 400
Acknowledgments 400
References 400
Part VI Display and Memory Applications 405
18 Oxide TFT Technology for Printed Electronics 407
Toshiaki Arai
18.1 OLEDs 407
18.1.1 OLED Displays 407
18.1.2 Organic Light-Emitting Diodes 408
18.1.3 Printed OLEDs 409
18.2 TFTs for OLED Driving 413
18.2.1 TFT Candidates 413
18.2.2 Pixel Circuits 413
18.2.3 Oxide TFTs 414
18.2.3.1 Bottom-Gate TFTs 415
18.2.3.2 Top-Gate TFTs 418
18.3 Oxide TFT-Driven Printed OLED Displays 424
18.4 Summary 427
References 428
19 Mechanically Flexible Nonvolatile Memory Thin-Film Transistors Using Oxide Semiconductor Active Channels on Ultrathin Polyimide Films 431
Sung-Min Yoon, Hyeong-Rae Kim, Hye-Won Jang, Ji-Hee Yang, Hyo-Eun Kim, and Sol-Mi Kwak
19.1 Introduction 431
19.2 Fabrication of Memory TFTs 432
19.2.1 Substrate Preparation 432
19.2.2 Device Fabrication Procedures 434
19.2.3 Characterization Methodologies 435
19.3 Device Operations of Flexible Memory TFTs 437
19.3.1 Optimization of Flexible IGZO-TFTs on PI Films 437
19.3.2 Nonvolatile Memory Operations of Flexible Memory TFTs 438
19.3.3 Operation Mechanisms and Device Physics 442
19.4 Choice of Alternative Materials 444
19.4.1 Introduction to Conducting Polymer Electrodes 444
19.4.2 Introduction of Polymeric Gate Insulators 446
19.5 Device Scaling to Vertical-Channel Structures 447
19.5.1 Vertical-Channel IGZO-TFTs on PI Films 447
19.5.2 Vertical-Channel Memory TFTs Using IGZO Channel and ZnO Trap Layers 449
19.6 Summary 453
19.6.1 Remaining Technical Issues 453
19.6.2 Conclusions and Outlooks 453
References 454
20 Amorphous Oxide Semiconductor TFTs for BEOL Transistor Applications 457
Nobuyoshi Saito and Keiji Ikeda
20.1 Introduction 457
20.2 Improvement of Immunity to H 2 Annealing 458
20.3 Increase of Mobility and Reduction of S/D Parasitic Resistance 463
20.4 Demonstration of Extremely Low Off-State Leakage Current Characteristics 467
References 471
21 Ferroelectric-HfO 2 Transistor Memory with IGZO Channels 473
Masaharu Kobayashi
21.1 Introduction 473
21.2 Device Operation and Design 475
21.3 Device Fabrication 478
21.4 Experimental Results and Discussions 479
21.4.1 FE-HfO 2 Capacitors with an IGZO Layer 479
21.4.2 IGZO Channel FeFETs 481
21.5 Summary 484
Acknowledgments 484
References 485
22 Neuromorphic Chips Using AOS Thin-Film Devices 487
Mutsumi Kimura
22.1 Introduction 487
22.2 Neuromorphic Systems with Crosspoint-Type ?-GTO Thin-Film Devices 488
22.2.1 Neuromorphic Systems 488
22.2.1.1 ?-GTO Thin-Film Devices 488
22.2.1.2 System Architecture 489
22.2.2 Experimental Results 492
22.3 Neuromorphic System Using an LSI Chip and ?-IGZO Thin-Film Devices [24] 493
22.3.1 Neuromorphic System 494
22.3.1.1 Neuron Elements 494
22.3.1.2 Synapse Elements 494
22.3.1.3 System Architecture 495
22.3.2 Working Principle 495
22.3.2.1 Cellular Neural Network 495
22.3.2.2 Tug-of-War Method 497
22.3.2.3 Modified Hebbian Learning 497
22.3.2.4 Majority-Rule Handling 498
22.3.3 Experimental Results 498
22.3.3.1 Raw Data 498
22.3.3.2 Associative Memory 499
22.4 Conclusion 499
Acknowledgments 500
References 500
23 Oxide TFTs and Their Application to X-Ray Imaging 503
Robert A. Street
23.1 Introduction 503
23.2 Digital X-Ray Detection and Imaging Modalities 504
23.2.1 Indirect Detection Imaging 504
23.2.2 Direct Detection Imaging 505
23.2.3 X-Ray Imaging Modalities 505
23.3 Oxide-TFT X-Ray Detectors 506
23.3.1 TFT Backplane Requirements for Digital X-Rays 506
23.3.2 An IGZO Detector Fabrication and Characterization 506
23.3.3 Other Reported Oxide X-Ray Detectors 509
23.4 How Oxide TFTs Can Improve Digital X-Ray Detectors 509
23.4.1 Noise and Image Quality in X-Ray Detectors 510
23.4.2 Minimizing Additive Electronic Noise with Oxides 510
23.4.3 Pixel Amplifier Backplanes 511
23.4.4 IGZO-TFT Noise 511
23.5 Radiation Hardness of Oxide TFTs 513
23.6 Oxide Direct Detector Materials 515
23.7 Summary 515
References 515
Part VII New Materials 519
24 Toward the Development of High-Performance p-Channel Oxide-TFTs and All-Oxide Complementary Circuits 521
Kenji Nomura
24.1 Introduction 521
24.2 Why Is High-Performance p-Channel Oxide Difficult? 521
24.3 The Current Development of p-Channel Oxide-TFTs 524
24.4 Comparisons of p-Type Cu 2 O and SnO Channels 526
24.5 Comparisons of the TFT Characteristics of Cu 2 O and SnO-TFTs 529
24.6 Subgap Defect Termination for p-Channel Oxides 532
24.7 All-Oxide Complementary Circuits 534
24.8 Conclusions 535
References 536
25 Solution-Synthesized Metal Oxides and Halides for Transparent p-Channel TFTs 539
Ao Liu, Huihui Zhu, and Yong-Young Noh
25.1 Introduction 539
25.2 Solution-Processed p-Channel Metal-Oxide TFTs 540
25.3 Transparent Copper(I) Iodide (CuI)-Based TFTs 546
25.4 Conclusions and Perspectives 548
Acknowledgments 549
References 549
26 Tungsten-Doped Active Layers for High-Mobility AOS-TFTs 553
Zhang Qun
26.1 Introduction 553
26.2 Advances in Tungsten-Doped High-Mobility AOS-TFTs 555
26.2.1 a-IWO-TFTs 555
26.2.2 a-IZWO-TFTs 562
26.2.3 Dual Tungsten-Doped Active-Layer TFTs 565
26.2.4 Treatment on the Backchannel Surface 566
26.3 Perspectives for High-Mobility AOS Active Layers 570
References 572
27 Rare Earth- and Transition Metal-Doped Amorphous Oxide Semiconductor Phosphors for Novel Light-Emitting Diode Displays 577
Keisuke Ide, Junghwan Kim, Hideo Hosono, and Toshio Kamiya
27.1 Introduction 577
27.2 Eu-Doped Amorphous Oxide Semiconductor Phosphor 577
27.3 Multiple-Color Emissions from Various Rare Earth-Doped AOS Phosphors 579
27.4 Transition Metal-Doped AOS Phosphors 582
References 584
28 Application of AOSs to Charge Transport Layers in Electroluminescent Devices 585
Junghwan Kim and Hideo Hosono
28.1 Electronic Structure and Electrical Properties of Amorphous Oxide Semiconductors (AOSs) 585
28.2 Criteria for Charge Transport Layers in Electroluminescent (EL) Devices 585
28.3 Amorphous Zn-Si-O Electron Transport Layers for Perovskite Light-Emitting Diodes (PeLEDs) 587
28.4 Amorphous In-Mo-O Hole Injection Layers for OLEDs 589
28.5 Perspective 594
References 595
29 Displays and Vertical-Cavity Surface-Emitting Lasers 597
Kenichi Iga
29.1 Introduction to Displays 597
29.2 Liquid Crystal Displays (LCDs) 597
29.2.1 History of LCDs 597
29.2.2 Principle of LCD: The TN Mode 598
29.2.3 Other LC Modes 600
29.2.4 Light Sources 600
29.2.5 Diffusion Plate and Light Guiding Layer 601
29.2.6 Microlens Arrays 601
29.2.7 Short-Focal-Length Projection 602
29.3 Organic EL Display 602
29.3.1 Method (a): Color-Coding Method 603
29.3.2 Method (b): Filter Method 603
29.3.3 Method (c): Blue Conversion Method 603
29.4 Vertical-Cavity Surface-Emitting Lasers 604
29.4.1 Motivation of Invention 604
29.4.2 What Is the Difference? 605
29.4.3 Device Realization 605
29.4.4 Applications 607
29.5 Laser Displays including VCSELs 607
29.5.1 Laser Displays 607
29.5.2 Color Gamut 608
29.5.3 Laser Backlight Method 609
Acknowledgments 610
References 611
Index 613
Series Editor's Foreword xvii
About the Editors xviii
List of Contributors xix
Part I Introduction 1
1.1 Transparent Amorphous Oxide Semiconductors for Display Applications 3
Hideo Hosono
1.1.1 Introduction to Amorphous Semiconductors as Thin-Film Transistor (TFT) Channels 3
1.1.2 Historical Overview 4
1.1.3 Oxide and Silicon 6
1.1.4 Transparent Amorphous Oxide Semiconductors 6
1.1.4.1 Electronic Structures 6
1.1.4.2 Materials 8
1.1.4.3 Characteristic Carrier Transport Properties 9
1.1.4.4 Electronic States 10
1.1.5 P-Type Oxide Semiconductors for Display Applications 13
1.1.5.1 Oxides of Transition Metal Cations with an Electronic Configuration of (n?1)d 10 ns 0 (n = 4or5) 13
1.1.5.2 Oxides of Metal Cations with an Electronic Configuration of ns 2 13
1.1.5.3 Oxides of Metal Cations with an Electronic Configuration of nd 6 14
1.1.6 Novel Amorphous Oxide Semiconductors 15
1.1.7 Summary and Outlook 17
References 18
1.2 Transparent Amorphous Oxide Semiconductors 21
Hideya Kumomi
1.2.1 Introduction 21
1.2.2 Technical Issues and Requirements of TFTs for AM-FPDs 21
1.2.2.1 Field-Effect Mobility 21
1.2.2.2 Off-State Leakage Current and On/Off Current Ratio 23
1.2.2.3 Stability and Reliability 23
1.2.2.4 Uniformity 23
1.2.2.5 Large-Area Devices by Large-Area Mother-Glass Substrates 24
1.2.2.6 Low-Temperature Fabrication and Flexibility 24
1.2.3 History, Features, Uniqueness, Development, and Applications of AOS-TFTs 24
1.2.3.1 History 24
1.2.3.2 Features and Uniqueness 25
1.2.3.3 Applications 27
1.2.3.4 Development and Products of AM-FPDs 28
1.2.4 Summary 29
References 30
Part II Fundamentals 31
2 Electronic Structure and Structural Randomness 33
Julia E. Medvedeva, Bishal Bhattarai, and D. Bruce Buchholz
2.1 Introduction 33
2.2 Brief Description of Methods and Approaches 35
2.2.1 Computational Approach 35
2.2.2 Experimental Approach 36
2.3 The Structure and Properties of Crystalline and Amorphous In 2 O 3 36
2.4 The Structure and Properties of Crystalline and Amorphous SnO 2 43
2.5 The Structure and Properties of Crystalline and Amorphous ZnO 46
2.6 The Structure and Properties of Crystalline and Amorphous Ga 2 O 3 52
2.7 Role of Morphology in Structure-Property Relationships 57
2.8 The Role of Composition in Structure-Property Relationships: IGO and IGZO 64
2.9 Conclusions 69
References 70
3 Electronic Structure of Transparent Amorphous Oxide Semiconductors 73
John Robertson and Zhaofu Zhang
3.1 Introduction 73
3.2 Mobility 73
3.3 Density of States 74
3.4 Band Structures of n-Type Semiconductors 78
3.5 Instabilities 81
3.6 Doping Limits and Finding Effective Oxide Semiconductors 86
3.7 OLED Electrodes 88
3.8 Summary 89
References 89
4 Defects and Relevant Properties 93
Toshio Kamiya, Kenji Nomura, Keisuke Ide, and Hideo Hosono
4.1 Introduction 93
4.2 Typical Deposition Condition 93
4.3 Overview of Electronic Defects in AOSs 94
4.4 Origins of Electron Donors 96
4.5 Oxygen- and Hydrogen-Related Defects and Near-VBM States 98
4.6 Summary 102
References 102
5 Amorphous Semiconductor Mobility Physics and TFT Modeling 105
John F. Wager
5.1 Amorphous Semiconductor Mobility: An Introduction 105
5.2 Diffusive Mobility 106
5.3 Density of States 110
5.4 TFT Mobility Considerations 111
5.5 TFT Mobility Extraction, Fitting, and Model Validation 112
5.6 Physics-Based TFT Mobility Modeling 118
5.7 Conclusions 121
References 122
6 Percolation Description of Charge Transport in Amorphous Oxide Semiconductors: Band Conduction Dominated by Disorder 125
A. V. Nenashev, F. Gebhard, K. Meerholz, and S. D. Baranovskii
6.1 Introduction 125
6.2 Band Transport via Extended States in the Random-Barrier Model (RBM) 126
6.2.1 Deficiencies of the Rate-Averaging Approach: Electrotechnical Analogy 127
6.2.2 Percolation Approach to Charge Transport in the RBM 129
6.3 Random Band-Edge Model (RBEM) for Charge Transport in AOSs 131
6.4 Percolation Theory for Charge Transport in the RBEM 133
6.4.1 From Regional to Global Conductivities in Continuum Percolation Theory 133
6.4.2 Averaging Procedure by Adler et al. 135
6.5 Comparison between Percolation Theory and EMA 136
6.6 Comparison with Experimental Data 137
6.7 Discussion and Conclusions 140
6.7.1 Textbook Description of Charge Transport in Traditional Crystalline Semiconductors (TCSs) 140
6.7.2 Results of This Chapter for Charge Transport in Amorphous Oxide Semiconductors (AOSs) 141
Acknowledgments 141
References 141
7 State and Role of Hydrogen in Amorphous Oxide Semiconductors 145
Hideo Hosono and Toshio Kamiya
7.1 Introduction 145
7.2 Concentration and Chemical States 145
7.3 Carrier Generation and Hydrogen 150
7.3.1 Carrier Generation by H Injection at Low Temperatures 150
7.3.2 Carrier Generation and Annihilation by Thermal Treatment 151
7.4 Energy Levels and Electrical Properties 153
7.5 Incorporation and Conversion of H Impurities 154
7.6 Concluding Remarks 155
Acknowledgments 156
References 156
Part III Processing 159
8 Low-Temperature Thin-Film Combustion Synthesis of Metal-Oxide Semiconductors: Science and Technology 161
Binghao Wang, Wei Huang, Antonio Facchetti, and Tobin J. Marks
8.1 Introduction 161
8.2 Low-Temperature Solution-Processing Methodologies 162
8.2.1 Alkoxide Precursors 162
8.2.2 Microwave-Assisted Annealing 165
8.2.3 High-Pressure Annealing 165
8.2.4 Photonic Annealing 165
8.2.4.1 Laser Annealing 166
8.2.4.2 Deep-Ultraviolet Illumination 168
8.2.4.3 Flash Lamp Annealing 170
8.2.5 Redox Reactions 170
8.3 Combustion Synthesis for MO TFTs 171
8.3.1 n-Type MO TFTs 172
8.3.2 p-Type MO TFTs 178
8.4 Summary and Perspectives 180
Acknowledgments 180
References 181
9 Solution-Processed Metal-Oxide Thin-Film Transistors for Flexible Electronics 185
Hyun Jae Kim
9.1 Introduction 185
9.2 Fundamentals of Solution-Processed Metal-Oxide Thin-Film Transistors 187
9.2.1 Deposition Methods for Solution-Processed Oxide Semiconductors 187
9.2.1.1 Coating-Based Deposition Methods 190
9.2.1.2 Printing-Based Deposition Methods 191
9.2.2 The Formation Mechanism of Solution-Processed Oxide Semiconductor Films 194
9.3 Low-Temperature Technologies for Active-Layer Engineering of Solution-Processed Oxide TFTs 196
9.3.1 Overview 196
9.3.2 Solution Modulation 197
9.3.2.1 Alkoxide Precursors 198
9.3.2.2 pH Adjustment 199
9.3.2.3 Combustion Reactions 199
9.3.2.4 Aqueous Solvent 199
9.3.3 Process Modulation 201
9.3.3.1 Photoactivation Process 201
9.3.3.2 High-Pressure Annealing (HPA) Process 202
9.3.3.3 Microwave-Assisted Annealing Process 204
9.3.3.4 Plasma-Assisted Annealing Process 204
9.3.4 Structure Modulation 205
9.3.4.1 Homojunction Dual-Active or Multiactive Layer 206
9.3.4.2 Heterojunction Dual- or Multiactive Layer 206
9.4 Applications of Flexible Electronics with Low-Temperature Solution-Processed Oxide TFTs 208
9.4.1 Flexible Displays 208
9.4.2 Flexible Sensors 208
9.4.3 Flexible Integrated Circuits 209
References 209
10 Recent Progress on Amorphous Oxide Semiconductor Thin-Film Transistors Using the Atomic Layer Deposition Technique 213
Hyun-Jun Jeong and Jin-Seong Park
10.1 Atomic Layer Deposition (ALD) for Amorphous Oxide Semiconductor (AOS) Applications 213
10.1.1 The ALD Technique 213
10.1.2 Research Motivation for ALD AOS Applications 215
10.2 AOS-TFTs Based on ALD 217
10.2.1 Binary Oxide Semiconductor TFTs Based on ALD 217
10.2.1.1 ZnO-TFTs 217
10.2.1.2 InOx-TFTs 218
10.2.1.3 SnOx-TFTs 218
10.2.2 Ternary and Quaternary Oxide Semiconductor TFTs Based on ALD 220
10.2.2.1 Indium-Zinc Oxide (IZO) and Indium-Gallium Oxide (IGO) 220
10.2.2.2 Zinc-Tin Oxide (ZTO) 223
10.2.2.3 Indium-Gallium-Zinc Oxide (IGZO) 223
10.2.2.4 Indium-Tin-Zinc Oxide (ITZO) 226
10.3 Challenging Issues of AOS Applications Using ALD 226
10.3.1 p-Type Oxide Semiconductors 226
10.3.1.1 Tin Monoxide (SnO) 228
10.3.1.2 Copper Oxide (cu x O) 229
10.3.2 Enhancing Device Performance: Mobility and Stability 230
10.3.2.1 Composition Gradient Oxide Semiconductors 230
10.3.2.2 Two-Dimensional Electron Gas (2DEG) Oxide Semiconductors 231
10.3.2.3 Spatial and Atmospheric ALD for Oxide Semiconductors 234
References 234
Part IV Thin-Film Transistors 239
11 Control of Carrier Concentrations in AOSs and Application to Bulk-Accumulation TFTs 241
Suhui Lee and Jin Jang
11.1 Introduction 241
11.2 Control of Carrier Concentration in a-IGZO 242
11.3 Effect of Carrier Concentration on the Performance of a-IGZO TFTs with a Dual-Gate Structure 247
11.3.1 Inverted Staggered TFTs 247
11.3.2 Coplanar TFTs 251
11.4 High-Drain-Current, Dual-Gate Oxide TFTs 252
11.5 Stability of Oxide TFTs: PBTS, NBIS, HCTS, Hysteresis, and Mechanical Strain 259
11.6 TFT Circuits: Ring Oscillators and Amplifier Circuits 266
11.7 Conclusion 270
References 270
12 Elevated-Metal Metal-Oxide Thin-Film Transistors: A Back-Gate Transistor Architecture with Annealing-Induced Source/Drain Regions 273
Man Wong, Zhihe Xia, and Jiapeng li
12.1 Introduction 273
12.1.1 Semiconducting Materials for a TFT 274
12.1.1.1 Amorphous Silicon 274
12.1.1.2 Low-Temperature Polycrystalline Silicon 274
12.1.1.3 MO Semiconductors 275
12.1.2 TFT Architectures 276
12.2 Annealing-Induced Generation of Donor Defects 279
12.2.1 Effects of Annealing on the Resistivity of IGZO 279
12.2.2 Microanalyses of the Thermally Annealed Samples 283
12.2.3 Lateral Migration of the Annealing-Induced Donor Defects 284
12.3 Elevated-Metal Metal-Oxide (EMMO) TFT Technology 286
12.3.1 Technology and Characteristics of IGZO EMMO TFTs 287
12.3.2 Applicability of EMMO Technology to Other MO Materials 291
12.3.3 Fluorinated EMMO TFTs 292
12.3.4 Resilience of Fluorinated MO against Hydrogen Doping 296
12.3.5 Technology and Display Resolution Trend 298
12.4 Enhanced EMMO TFT Technologies 301
12.4.1 3-EMMO TFT Technology 302
12.4.2 Self-Aligned EMMO TFTs 307
12.5 Conclusion 309
Acknowledgments 310
References 310
13 Hot Carrier Effects in Oxide-TFTs 315
Mami N. Fujii, Takanori Takahashi, Juan Paolo Soria Bermundo, and Yukiharu Uraoka
13.1 Introduction 315
13.2 Analysis of Hot Carrier Effect in IGZO-TFTs 315
13.2.1 Photoemission from IGZO-TFTs 315
13.2.2 Kink Current in Photon Emission Condition 318
13.2.3 Hot Carrier-Induced Degradation of a-IGZO-TFTs 318
13.3 Analysis of the Hot Carrier Effect in High-Mobility Oxide-TFTs 322
13.3.1 Bias Stability under DC Stresses in a High-Mobility IWZO-TFT 322
13.3.2 Analysis of Dynamic Stress in Oxide-TFTs 323
13.3.3 Photon Emission from the IWZO-TFT under Pulse Stress 323
13.4 Conclusion 328
References 328
14 Carbon-Related Impurities and NBS Instability in AOS-TFTs 333
Junghwan Kim and Hideo Hosono
14.1 Introduction 333
14.2 Experimental 334
14.3 Results and Discussion 334
14.4 Summary 337
References 339
Part V TFTs and Circuits 341
15 Oxide TFTs for Advanced Signal-Processing Architectures 343
Arokia Nathan, Denis Striakhilev, and Shuenn-Jiun Tang
15.1 Introduction 343
15.1.1 Device-Circuit Interactions 343
15.2 Above-Threshold TFT Operation and Defect Compensation: AMOLED Displays 345
15.2.1 AMOLED Display Challenges 345
15.2.2 Above-Threshold Operation 347
15.2.3 Temperature Dependence 347
15.2.4 Effects of Process-Induced Spatial Nonuniformity 349
15.2.5 Overview of External Compensation for AMOLED Displays 351
15.3 Ultralow-Power TFT Operation in a Deep Subthreshold (Near Off-State) Regime 354
15.3.1 Schottky Barrier TFTs 355
15.3.2 Device Characteristics and Small Signal Parameters 358
15.3.3 Common Source Amplifier 360
15.4 Oxide TFT-Based Image Sensors 362
15.4.1 Heterojunction Oxide Photo-TFTs 362
15.4.2 Persistent Photocurrent 364
15.4.3 All-Oxide Photosensor Array 365
References 366
16 Device Modeling and Simulation of TAOS-TFTs 369
Katsumi Abe
16.1 Introduction 369
16.2 Device Models for TAOS-TFTs 369
16.2.1 Mobility Model 369
16.2.2 Density of Subgap States (DOS) Model 371
16.2.3 Self-Heating Model 372
16.3 Applications 373
16.3.1 Temperature Dependence 373
16.3.2 Channel-Length Dependence 373
16.3.3 Channel-Width Dependence 375
16.3.4 Dual-Gate Structure 378
16.4 Reliability 379
16.5 Summary 381
Acknowledgments 381
References 382
17 Oxide Circuits for Flexible Electronics 383
Kris Myny, Nikolaos Papadopoulos, Florian De Roose, and Paul Heremans
17.1 Introduction 383
17.2 Technology-Aware Design Considerations 383
17.2.1 Etch-Stop Layer, Backchannel Etch, and Self-Aligned Transistors 384
17.2.1.1 Etch-Stop Layer 384
17.2.1.2 Backchannel Etch 385
17.2.1.3 Self-Aligned Transistors 385
17.2.1.4 Comparison 386
17.2.2 Dual-Gate Transistors 386
17.2.2.1 Stack Architecture 386
17.2.2.2 Effect of the Backgate 388
17.2.3 Moore's Law for TFT Technologies 389
17.2.3.1 Cmos 389
17.2.3.2 Thin-Film Electronics Historically 389
17.2.3.3 New Drivers for Thin-Film Scaling: Circuits 390
17.2.3.4 L-Scaling 391
17.2.3.5 W and L Scaling 391
17.2.3.6 Overall Lateral Scaling 391
17.2.3.7 Oxide Thickness and Supply Voltage Scaling 391
17.2.4 Conclusion 392
17.3 Digital Electronics 392
17.3.1 Communication Chips 392
17.3.2 Complex Metal-Oxide-Based Digital Chips 395
17.4 Analog Electronics 396
17.4.1 Thin-Film ADC Topologies 396
17.4.2 Imager Readout Peripherals 397
17.4.3 Healthcare Patches 399
17.5 Summary 400
Acknowledgments 400
References 400
Part VI Display and Memory Applications 405
18 Oxide TFT Technology for Printed Electronics 407
Toshiaki Arai
18.1 OLEDs 407
18.1.1 OLED Displays 407
18.1.2 Organic Light-Emitting Diodes 408
18.1.3 Printed OLEDs 409
18.2 TFTs for OLED Driving 413
18.2.1 TFT Candidates 413
18.2.2 Pixel Circuits 413
18.2.3 Oxide TFTs 414
18.2.3.1 Bottom-Gate TFTs 415
18.2.3.2 Top-Gate TFTs 418
18.3 Oxide TFT-Driven Printed OLED Displays 424
18.4 Summary 427
References 428
19 Mechanically Flexible Nonvolatile Memory Thin-Film Transistors Using Oxide Semiconductor Active Channels on Ultrathin Polyimide Films 431
Sung-Min Yoon, Hyeong-Rae Kim, Hye-Won Jang, Ji-Hee Yang, Hyo-Eun Kim, and Sol-Mi Kwak
19.1 Introduction 431
19.2 Fabrication of Memory TFTs 432
19.2.1 Substrate Preparation 432
19.2.2 Device Fabrication Procedures 434
19.2.3 Characterization Methodologies 435
19.3 Device Operations of Flexible Memory TFTs 437
19.3.1 Optimization of Flexible IGZO-TFTs on PI Films 437
19.3.2 Nonvolatile Memory Operations of Flexible Memory TFTs 438
19.3.3 Operation Mechanisms and Device Physics 442
19.4 Choice of Alternative Materials 444
19.4.1 Introduction to Conducting Polymer Electrodes 444
19.4.2 Introduction of Polymeric Gate Insulators 446
19.5 Device Scaling to Vertical-Channel Structures 447
19.5.1 Vertical-Channel IGZO-TFTs on PI Films 447
19.5.2 Vertical-Channel Memory TFTs Using IGZO Channel and ZnO Trap Layers 449
19.6 Summary 453
19.6.1 Remaining Technical Issues 453
19.6.2 Conclusions and Outlooks 453
References 454
20 Amorphous Oxide Semiconductor TFTs for BEOL Transistor Applications 457
Nobuyoshi Saito and Keiji Ikeda
20.1 Introduction 457
20.2 Improvement of Immunity to H 2 Annealing 458
20.3 Increase of Mobility and Reduction of S/D Parasitic Resistance 463
20.4 Demonstration of Extremely Low Off-State Leakage Current Characteristics 467
References 471
21 Ferroelectric-HfO 2 Transistor Memory with IGZO Channels 473
Masaharu Kobayashi
21.1 Introduction 473
21.2 Device Operation and Design 475
21.3 Device Fabrication 478
21.4 Experimental Results and Discussions 479
21.4.1 FE-HfO 2 Capacitors with an IGZO Layer 479
21.4.2 IGZO Channel FeFETs 481
21.5 Summary 484
Acknowledgments 484
References 485
22 Neuromorphic Chips Using AOS Thin-Film Devices 487
Mutsumi Kimura
22.1 Introduction 487
22.2 Neuromorphic Systems with Crosspoint-Type ?-GTO Thin-Film Devices 488
22.2.1 Neuromorphic Systems 488
22.2.1.1 ?-GTO Thin-Film Devices 488
22.2.1.2 System Architecture 489
22.2.2 Experimental Results 492
22.3 Neuromorphic System Using an LSI Chip and ?-IGZO Thin-Film Devices [24] 493
22.3.1 Neuromorphic System 494
22.3.1.1 Neuron Elements 494
22.3.1.2 Synapse Elements 494
22.3.1.3 System Architecture 495
22.3.2 Working Principle 495
22.3.2.1 Cellular Neural Network 495
22.3.2.2 Tug-of-War Method 497
22.3.2.3 Modified Hebbian Learning 497
22.3.2.4 Majority-Rule Handling 498
22.3.3 Experimental Results 498
22.3.3.1 Raw Data 498
22.3.3.2 Associative Memory 499
22.4 Conclusion 499
Acknowledgments 500
References 500
23 Oxide TFTs and Their Application to X-Ray Imaging 503
Robert A. Street
23.1 Introduction 503
23.2 Digital X-Ray Detection and Imaging Modalities 504
23.2.1 Indirect Detection Imaging 504
23.2.2 Direct Detection Imaging 505
23.2.3 X-Ray Imaging Modalities 505
23.3 Oxide-TFT X-Ray Detectors 506
23.3.1 TFT Backplane Requirements for Digital X-Rays 506
23.3.2 An IGZO Detector Fabrication and Characterization 506
23.3.3 Other Reported Oxide X-Ray Detectors 509
23.4 How Oxide TFTs Can Improve Digital X-Ray Detectors 509
23.4.1 Noise and Image Quality in X-Ray Detectors 510
23.4.2 Minimizing Additive Electronic Noise with Oxides 510
23.4.3 Pixel Amplifier Backplanes 511
23.4.4 IGZO-TFT Noise 511
23.5 Radiation Hardness of Oxide TFTs 513
23.6 Oxide Direct Detector Materials 515
23.7 Summary 515
References 515
Part VII New Materials 519
24 Toward the Development of High-Performance p-Channel Oxide-TFTs and All-Oxide Complementary Circuits 521
Kenji Nomura
24.1 Introduction 521
24.2 Why Is High-Performance p-Channel Oxide Difficult? 521
24.3 The Current Development of p-Channel Oxide-TFTs 524
24.4 Comparisons of p-Type Cu 2 O and SnO Channels 526
24.5 Comparisons of the TFT Characteristics of Cu 2 O and SnO-TFTs 529
24.6 Subgap Defect Termination for p-Channel Oxides 532
24.7 All-Oxide Complementary Circuits 534
24.8 Conclusions 535
References 536
25 Solution-Synthesized Metal Oxides and Halides for Transparent p-Channel TFTs 539
Ao Liu, Huihui Zhu, and Yong-Young Noh
25.1 Introduction 539
25.2 Solution-Processed p-Channel Metal-Oxide TFTs 540
25.3 Transparent Copper(I) Iodide (CuI)-Based TFTs 546
25.4 Conclusions and Perspectives 548
Acknowledgments 549
References 549
26 Tungsten-Doped Active Layers for High-Mobility AOS-TFTs 553
Zhang Qun
26.1 Introduction 553
26.2 Advances in Tungsten-Doped High-Mobility AOS-TFTs 555
26.2.1 a-IWO-TFTs 555
26.2.2 a-IZWO-TFTs 562
26.2.3 Dual Tungsten-Doped Active-Layer TFTs 565
26.2.4 Treatment on the Backchannel Surface 566
26.3 Perspectives for High-Mobility AOS Active Layers 570
References 572
27 Rare Earth- and Transition Metal-Doped Amorphous Oxide Semiconductor Phosphors for Novel Light-Emitting Diode Displays 577
Keisuke Ide, Junghwan Kim, Hideo Hosono, and Toshio Kamiya
27.1 Introduction 577
27.2 Eu-Doped Amorphous Oxide Semiconductor Phosphor 577
27.3 Multiple-Color Emissions from Various Rare Earth-Doped AOS Phosphors 579
27.4 Transition Metal-Doped AOS Phosphors 582
References 584
28 Application of AOSs to Charge Transport Layers in Electroluminescent Devices 585
Junghwan Kim and Hideo Hosono
28.1 Electronic Structure and Electrical Properties of Amorphous Oxide Semiconductors (AOSs) 585
28.2 Criteria for Charge Transport Layers in Electroluminescent (EL) Devices 585
28.3 Amorphous Zn-Si-O Electron Transport Layers for Perovskite Light-Emitting Diodes (PeLEDs) 587
28.4 Amorphous In-Mo-O Hole Injection Layers for OLEDs 589
28.5 Perspective 594
References 595
29 Displays and Vertical-Cavity Surface-Emitting Lasers 597
Kenichi Iga
29.1 Introduction to Displays 597
29.2 Liquid Crystal Displays (LCDs) 597
29.2.1 History of LCDs 597
29.2.2 Principle of LCD: The TN Mode 598
29.2.3 Other LC Modes 600
29.2.4 Light Sources 600
29.2.5 Diffusion Plate and Light Guiding Layer 601
29.2.6 Microlens Arrays 601
29.2.7 Short-Focal-Length Projection 602
29.3 Organic EL Display 602
29.3.1 Method (a): Color-Coding Method 603
29.3.2 Method (b): Filter Method 603
29.3.3 Method (c): Blue Conversion Method 603
29.4 Vertical-Cavity Surface-Emitting Lasers 604
29.4.1 Motivation of Invention 604
29.4.2 What Is the Difference? 605
29.4.3 Device Realization 605
29.4.4 Applications 607
29.5 Laser Displays including VCSELs 607
29.5.1 Laser Displays 607
29.5.2 Color Gamut 608
29.5.3 Laser Backlight Method 609
Acknowledgments 610
References 611
Index 613
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