Nitride Semiconductor Light-Emitting Diodes (LEDs)

Prof. JianJang Huang received the B.S. degree in Electrical Engineering (EE) and the M.S. degree in Graduate Institute of Photonics and Optoelectronics (GIPO) from National Taiwan University (NTU), Taipei, Taiwan, in 1994 and 1996, respectively, and the Ph.D. degree in Electrical Engineering from the University of Illinois, Urbana-Champaign, in 2002. He had worked with WJ (Watkins Johnson) Communications in California, as a Staff Scientist from 2002 to 2004. He then came back to Taiwan in 2004 and is currently the professor at NTU EE and GIPO.Prof. Huang has been involved in the development of optoelectronic and electronic devices. He has developed a spin-coating method for nanosphere lithography (NSL) to significantly improve the performance of light emitting diodes (LEDs), solar cells and nanorod devices. His NSL approach has been licensed to several LED companies in Taiwan. He has also fabricated and characterized IGZO TFTs and the corresponding circuits on glass and flexible substrates. In recent years, his group has spent great efforts in realizing cancer cell probes using ZnO nanorods, and high-sensitivity protein sensors based on IGZO TFTs.Prof. Huang is a member of the Phi Tau Phi Scholastic Honor Society. He received “Wu Da-Yu” award in 2008, the most prestigious one for young researchers in Taiwan sponsored by National Science Council. And in the same year, he received the award for the most excellent young electrical engineer from the Chinese Institute of Electrical Engineering. He has served in several IPO committees in Taiwan Stock Exchange. He is currently the board director of GCS holdings in Torrance, CA, USA and the conference chair of SPIE, International Conference on Solid-State Lighting. Professor H. C. Kuo received the B.S. degree in Physics from National Taiwan University, Taiwan the M.S. degree in Electrical and computer engineering from Rutgers University in 1995, and the Ph.D. from Center of Compound Semiconductor Microelectronics (CCSM) of University of Illinois- Urbana Champaign in 1998. He has an extensive professional career both in research and industrial research institutions that includes: Research Consultant in Lucent Technologies, Bell Lab (1995-97); Member of Technical Staff in Fiber-optics Division at Agilent Technologies, USA (1999-2001) and Manager of LuxNet Corporation, USA (2001-2002). Since October, 2002 he joined National Chiao Tung University as a faculty member of Institute of Electro-Optical Engineering. Professor Kuo is a member of the IEEE and a recipient of Yang faculty Award from the Foundation for the Advancement of Outstanding Scholarship, he was author and co-author of 70 SCI journal papers and 80 international conference papers. Shyh-Chiang Shen received his B.S. and M.S. degrees, both in electrical engineering, from National Taiwan University in 1993 and 1995, respectively. He received his Ph.D. degree in electrical engineering at the University of Illinois at Urbana-Champaign (UIUC) in 2001. During his graduate study at the University of Illinois, he was involved in the development of low-voltage RF MEMS switches and ion-implanted GaAs MESFET using e-beam direct gate-writing photolithography techniques.Dr. Shen joined Xindium Technologies, Inc. as a senior processing engineer in June 2001. He developed a proprietary high-performance InP SHBT technology for 40Gb/s OEIC applications and InP-based power HBT technology for wireless communications. In August 2004, he joined the HSIC group at the University of Illinois as a postdoctoral research associate to work on exciting research projects. In January 2005, he joined the Georgia Institute of Technology as an Assistant Professor. Dr. Shen holds 7 awarded U.S. patents in the MEMS and microelectronics areas. His current research is focused on wide bandgap semiconductor microelectronics and optoelectronic devices for high-energy-efficiency applications.

• Contributor contact detailsWoodhead Publishing Series in Electronic and Optical MaterialsDedicationPrefacePart I: Materials and fabrication1: Molecular beam epitaxy (MBE) growth of nitride semiconductorsAbstract1.1 Introduction1.2 Molecular beam epitaxial (MBE) growth techniques1.3 Plasma-assisted MBE (PAMBE) growth of nitride epilayers and quantum structures1.4 Nitride nanocolumn (NC) materials1.5 Nitride nanostructures based on NCs1.6 Conclusion2: Modern metal-organic chemical vapor deposition (MOCVD) reactors and growing nitride-based materialsAbstract2.1 Introduction2.2 MOCVD systems2.3 Planetary reactors2.4 Close-coupled showerhead (CCS) reactors2.5 In situ monitoring systems and growing nitride-based materials2.6 Acknowledgements3: Gallium nitride (GaN) on sapphire substrates for visible LEDsAbstract3.1 Introduction3.2 Sapphire substrates3.3 Strained heteroepitaxial growth on sapphire substrates3.4 Epitaxial overgrowth of GaN on sapphire substrates3.5 GaN growth on non-polar and semi-polar surfaces3.6 Future trends4: Gallium nitride (GaN) on silicon substrates for LEDsAbstract4.1 Introduction4.2 An overview of gallium nitride (GaN) on silicon substrates4.3 Silicon overview4.4 Challenges for the growth of GaN on silicon substrates4.5 Buffer-layer strategies4.6 Device technologies4.7 Conclusion5: Phosphors for white LEDsAbstract5.1 Introduction5.2 Optical transitions of Ce3 + and Eu2 +5.3 Chemical composition of representative nitride and oxynitride phosphors5.4 Compounds activated by Eu2 +5.5 Compounds activated by Ce3 +5.6 Features of the crystal structure of nitride and oxynitride phosphors5.7 Features of optical transitions of nitride and oxynitride phosphors5.8 Conclusion and future trends5.9 Acknowledgements6: Fabrication of nitride LEDsAbstract6.1 Introduction6.2 GaN-based flip-chip LEDs and flip-chip technology6.3 GaN FCLEDs with textured micro-pillar arrays6.4 GaN FCLEDs with a geometric sapphire shaping structure6.5 GaN thin-film photonic crystal (PC) LEDs6.6 PC nano-structures and PC LEDs6.7 Light emission characteristics of GaN PC TFLEDs6.8 Conclusion7: Nanostructured LEDsAbstract7.1 Introduction7.2 General mechanisms for growth of gallium nitride (GaN) related materials7.3 General characterization method7.4 Top-down technique for nanostructured LEDs7.5 Bottom-up technique for GaN nanopillar substrates prepared by molecular beam epitaxy7.6 Conclusion8: Nonpolar and semipolar LEDsAbstract8.1 Motivation: limitations of conventional c-plane LEDs8.2 Introduction to selected nonpolar and semipolar planes8.3 Challenges in nonpolar and semipolar epitaxial growth8.4 Light extraction for nonpolar and semipolar LEDsPart II: Performance of nitride LEDs9: Efficiency droop in gallium indium nitride (GaInN)/gallium nitride (GaN) LEDsAbstract9.1 Introduction9.2 Recombination models in LEDs9.3 Thermal roll-over in gallium indium nitride (GaInN) LEDs9.4 Auger recombination9.5 High-level injection and the asymmetry of carrier concentration and mobility9.6 Non-capture of carriers9.7 Polarization fields9.8 Carrier delocalization9.9 Discussion and comparison of droop mechanisms9.10 Methods for overcoming droop10: Photonic crystal nitride LEDsAbstract10.1 Introduction10.2 Photonic crystal (PC) technology10.3 Improving LED extraction efficiency through PC surface patterning10.4 PC-enhanced light extraction in P-side up LEDs10.5 Modelling PC-LEDs10.6 P-side up PC-LED performance10.7 PC-enhanced light extraction in N-side up LEDs10.8 Summary10.9 Conclusions11: Surface plasmon enhanced LEDsAbstract11.1 Introduction11.2 Mechanism for plasmon-coupled emission11.3 Fabrication of plasmon-coupled nanostructures11.4 Performance and outlook11.5 Acknowledgements12: Nitride LEDs based on quantum wells and quantum dotsAbstract12.1 Light-emitting diodes (LEDS)12.2 Polarization effects in III-nitride LEDs12.3 Current status of III-nitride LEDs12.4 Modern LED designs and enhancements13: Color tunable LEDsAbstract13.1 Introduction13.2 Initial idea for stacked LEDs13.3 Second-generation LED stack with inclined sidewalls13.4 Third-generation tightly integrated chip-stacking approach13.5 Group-addressable pixelated micro-LED arrays13.6 Conclusions14: Reliability of nitride LEDsAbstract14.1 Introduction14.2 Reliability testing of nitride LEDs14.3 Evaluation of LED degradation14.4 Degradation mechanisms14.5 Conclusion15: Chip packaging: encapsulation of nitride LEDsAbstract15.1 Functions of LED chip packaging15.2 Basic structure of LED packaging modules15.3 Processes used in LED packaging15.4 Optical effects of gold wire bonding15.5 Optical effects of phosphor coating15.6 Optical effects of freeform lenses15.7 Thermal design and processing of LED packaging15.8 ConclusionPart III: Applications of nitride LEDs16: White LEDs for lighting applications: the role of standardsAbstract16.1 General lighting applications16.2 LED terminology16.3 Copying traditional lamps?16.4 Freedom of choice16.5 Current and future trends17: Ultraviolet LEDsAbstract17.1 Research background of deep ultraviolet (DUV) LEDs17.2 Growth of low threading dislocation density (TDD) AlN layers on sapphire17.3 Marked increases in internal quantum efficiency (IQE)17.4 Aluminum gallium nitride (AlGaN)-based DUV-LEDs fabricated on high-quality aluminum nitride (AlN)17.5 Increase in electron injection efficiency (EIE) and light extraction efficiency (LEE)17.6 Conclusions and future trends18: Infrared emitters made from III-nitride semiconductorsAbstract18.1 Introduction18.2 High indium (In) content alloys for infrared emitters18.3 Rare-earth (RE) doped gallium nitride (GaN) emitters18.4 III-nitride materials for intersubband (ISB) optoelectronics18.5 ISB devices18.6 Conclusions18.7 Acknowledgements19: LEDs for liquid crystal display (LCD) backlightingAbstract19.1 Introduction19.2 Types of LED LCD backlighting units (BLUs)19.3 Technical considerations for optical films and plates19.4 Requirements for LCD BLUs19.5 Advantages and history of LED BLUs19.6 Market trends and technological developments19.7 Optical design20: LEDs in automotive lightingAbstract20.1 Introduction20.2 Forward lighting20.3 Signal lighting20.4 Human factor issues with LEDs20.5 Energy and environmental issues20.6 Future trends20.7 Sources of further information and advice20.8 AcknowledgmentsIndex