r^a light-emitting diodes (LEDs) Nitride semiconductor Materials, technologies and applications JianJang Huang, Hao-Chung Kuo and Shyh-Chiang Shen

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1 Woodhead Publishing Series in Electronic and Optical Materials: Number 54 Nitride semiconductor light-emitting diodes (LEDs) Materials, technologies and applications Edited by JianJang Huang, Hao-Chung Kuo and Shyh-Chiang Shen WP WOODHEAD PUBLISHING r^a Oxford Cambridge Philadelphia New Delhi

2 Contents Contributor contact details Woodhead Publishing Series in Electronic and Optical Materials Preface xiii xvii xxiii Part I Materials and fabrication 1 1 Molecular beam epitaxy (MBE) growth of nitride semiconductors 3 Q.-D. Zhuang, Lancaster University, UK 1.1 Introduction Molecular beam epitaxial (MBE) growth techniques Plasma-assisted MBE (PAMBE) growth of nitride epilayers and quantum structures Nitride nanocolumn (NC) materials Nitride nanostructures based on NCs Conclusion References 21 2 Modern metal-organic chemical vapor deposition (MOCVD) reactors and growing nitride-based materials 27 F. H. Yang, AIXTRON Taiwan Co Ltd, Taiwan 2.1 Introduction MOCVD systems Planetary reactors Close-coupled showerhead (CCS) reactors In situ monitoring systems and growing nitride-based materials Acknowledgements References 65 v

3 vi Contents 3 Gallium nitride (GaN) on sapphire substrates for visible LEDs 66 J.-H. Ryou, University of Houston, USA 3.1 Introduction Sapphire substrates Strained heteroepitaxial growth on sapphire substrates Epitaxial overgrowth of GaN on sapphire substrates GaN growth on non-polar and semi-polar surfaces Future trends References 89 4 Gallium nitride (GaN) on silicon substrates for LEDs 99 M. H. Kane, Texas A & M University at Galveston, USA and N. Arefin, University of Oklahoma, USA 4.1 Introduction An overview of gallium nitride (GaN) on silicon substrates Silicon overview Challenges for the growth of GaN on silicon substrates Buffer-layer strategies Device technologies Conclusion References Phosphors for white LEDs 144 H. Yamamoto, formerly of Tokyo University of Technology, Japan and T. Yamamoto, Ajinomoto Pharmaceuticals Co, Ltd, Japan 5.1 Introduction Optical transitions of Ce3+and Eu Chemical composition of representative nitride and oxynitride phosphors Compounds activated by Eu Compounds activated by Ce Features of the crystal structure of nitride and oxynitride phosphors Features of optical transitions of nitride and oxynitride phosphors Conclusion and future trends Acknowledgements References Fabrication of nitride LEDs 181 R.-H. Horng, D.-S. Wuu and C.-F. Lin, National Chung Hsing University, Taiwan and C.-F. Lai, Feng-Chia University, Taiwan 6.1 Introduction 181

4 Contents vii 6.2 GaN-based flip-chip LEDs and flip-chip technology GaN FCLEDs with textured micro-pillar arrays GaN FCLEDs with a geometric sapphire shaping structure GaN thin-film photonic crystal (PC) LEDs PC nano-structures and PC LEDs Light emission characteristics of GaN PC TFLEDs Conclusion References Nanostructured LEDs 216 C. -C. Lin, D. W. Lin, C.-H. Chiu, Z. Y. Li and Y. P. Lan, National Chiao Tung University, Taiwan, J. J. Huang, National Taiwan University, Taiwan and H.-C. Kuo, National Chiao Tung University, Taiwan 7.1 Introduction General mechanisms for growth of gallium nitride (GaN) related materials General characterization method Top-down technique for nanostructured LEDs Bottom-up technique for GaN nanopillar substrates prepared by molecular beam epitaxy Conclusion References Nonpolar and semipolar LEDs 250 Y.-R. Wu, National Taiwan University, Taiwan, C.-Y. Huang, TSMC Solid State Lighting, Ltd, Taiwan, and Y. Zhao and J. S. Speck, University of California, Santa Barbara, USA 8.1 Motivation: limitations of conventional c-plane LEDs Introduction to selected nonpolar and semipolar planes Challenges in nonpolar and semipolar epitaxial growth Light extraction for nonpolar and semipolar LEDs References 270 Part II Performance of nitride LEDs Efficiency droop in gallium indium nitride (GalnN)/gallium nitride (GaN) LEDs 279 D. S. Meyaard, G.-B. Lin, J. Cho and E. F. Schubert, Rensselaer Polytechnic Institute, USA 9.1 Introduction Recombination models in LEDs Thermal roll-over in gallium indium nitride (GalnN) LEDs Auger recombination 284

5 viii Contents 9.5 High-level injection and the asymmetry of carrier concentration and mobility Non-capture of carriers Polarization fields Carrier derealization Discussion and comparison of droop mechanisms Methods for overcoming droop References Photonic crystal nitride LEDs 301 M. D. B. Charlton, University of Southampton, UK 10.1 Introduction Photonic crystal (PC) technology Improving LED extraction efficiency through PC surface patterning PC-enhanced light extraction in P-side up LEDs Modelling PC-LEDs P-side up PC-LED performance PC-enhanced light extraction in N-side up LEDs Summary Conclusions References Surface plasmon enhanced LEDs 355 Q. Hao and T. Qiu, Southeast University, China and P. K. Chu, City University of Hong Kong, China 11.1 Introduction Mechanism for plasmon-coupled emission Fabrication of plasmon-coupled nanostructures Performance and outlook Acknowledgements References Nitride LEDs based on quantum wells and quantum dots 368 J. Verma, A. Verma, V. Protasenko, S. M. Islam and D. Jena, University of Notre Dame, USA 12.1 Light-emitting diodes (LEDs) Polarization effects in IH-nitride LEDs Current status of Ill-nitride LEDs Modern LED designs and enhancements References 400

6 Contents ix 13 Color tunable LEDs 409 Y. F. Cheung, Z. Ma and H. W. Choi, The University of Hong Kong, People's Republic of China 13.1 Introduction Initial idea for stacked LEDs Second-generation LED stack with inclined sidewalls Third-generation tightly-integrated chip-stacking approach Group-addressable pixelated micro-led arrays Conclusions References Reliability of nitride LEDs 428 T.-T. Chen, C.-F. Dai, C.-P. Wang, H.-K. Fu, P.-T. Chou and W. Y. Yeh, Industrial Technology Research Institute (ITRI), Taiwan 14.1 Introduction Reliability testing of nitride LEDs Evaluation of LED degradation Degradation mechanisms Conclusion References Chip packaging: encapsulation of nitride LEDs 441 X. Luo and R. Hu, Huazhong University of Science and Technology, People's Republic of China 15.1 Functions of LED chip packaging Basic structure of LED packaging modules Processes used in LED packaging Optical effects of gold wire bonding Optical effects of phosphor coating Optical effects of freeform lenses Thermal design and processing of LED packaging Conclusion References 476 Part III Applications of nitride LEDs White LEDs for lighting applications: the role of standards 485 R. Kotschenreuther, OSRAM GmbH, Germany 16.1 General lighting applications LED terminology Copying traditional lamps? 490

7 x Contents 16.4 Freedom ofchoice Current and future trends References Ultraviolet LEDs 497 H. Hirayama, RIKEN, Japan 17.1 Research background of deep ultraviolet (DUV) LEDs Growth of low threading dislocation density (TDD) A1N layers on sapphire Marked increases in internal quantum efficiency (IQE) Aluminum gallium nitride (AlGaN)-based DUV-LEDs fabricated on high-quality aluminum nitride (A1N) Increase in electron injection efficiency (EIE) and light extraction efficiency (LEE) Conclusions and future trends References Infrared emitters made from Ill-nitride semiconductors 533 Y. Kotsar and E. Monroy, CEA-Grenoble, INAC/SP2M/NPSC, France 18.1 Introduction High indium (In) content alloys for infrared emitters Rare-earth (RE) doped gallium nitride (GaN) emitters Ill-nitride materials for intersubband (ISB) optoelectronics ISB devices Conclusions Acknowledgements References LEDs for liquid crystal display (LCD) backlighting 566 C.-F. Chen, National Central University, Taiwan 19.1 Introduction Types of LED LCD backlighting units (BLUs) Technical considerations for optical films and plates Requirements for LCD BLUs Advantages and history of LED BLUs Market trends and technological developments Optical design References LEDs in automotive lighting 595 J. D. Bullough, Rensselaer Polytechnic Institute, USA 20.1 Introduction 595

8 Contents xi 20.2 Forward lighting Signal lighting Human factor issues with LEDs Energy and environmental issues Future trends Sources offurther information and advice Acknowledgments References 604 Index 607