METALORGANIC CHEMICAL VAPOR DEPOSITION OF GALLIUM NITRIDE ON SACRIFICIAL SUBSTRATES A Dissertation Presented to The Academic Faculty By William Edward Fenwick In Partial Fulfillment Of the Requirements for the Degree Doctor of Philosophy in the School of Electrical and Computer Engineering Georgia Institute of Technology August, 2009 Copyright © William Edward Fenwick, 2009 Metalorganic Chemical Vapor Deposition of Gallium Nitride on Sacrificial Substrates Approved by: Ian T. Ferguson, Advisor Abdallah Ougazzaden, Co-advisor Electrical and Computer Engineering Electrical and Computer Engineering Materials Science and Engineering Georgia Institute of Technology Georgia Institute of Technology Benjamin D.B. Klein Joseph L.A. Hughes Electrical and Computer Engineering Electrical and Computer Engineering Georgia Institute of Technology Georgia Institute of Technology Linda Milor Nazanin Bassiri-Gharb Electrical and Computer Engineering Mechanical Engineering Georgia Institute of Technology Materials Science and Engineering Georgia Institute of Technology Date Approved: June 8, 2009 “If we knew what we were doing, it would not be called research, would it?” -Albert Einstein To my grandfather, ‘Pop’… ACKNOWLEDGEMENTS I would like to thank my advisor, Prof. Ian Ferguson, for his support and encouragement, and my co-advisor, Prof. Abdallah Ougazzaden, for his guidance. I would also like to thank the members, past and present, of the Solid State Lighting/MOCVD group at Georgia Tech including, but not limited to, Dr. Vincent Woods, Dr. Martin Strassburg, Dr. Ming Pan, Dr. Adam Payne, Dr. Eun Hyun Park, Dr. Shen-Jie Wang, Dr. Hongbo Hu, Dr. David Nicol, Dr. Matthew Kane, Dr. Hun Kang, Dr. Shalini Gupta, Dr. Omkar Jani, Dr. Muhammad Jamil, Dr. Enno Malguth, Dr. Nola Li, Ali Asghar, Andrew Melton, Tahir Zaidi, Tianming Xu, Balakrishnam Jampana, Peter Speirs, Olivier Hamard, Petko Petkov, and Yong Huang for their support and team work. Angela Yvonne also deserves special acknowledgement for all of her time and administrative support. I am grateful to Dr. Nikolaus Dietz at Georgia State University for his guidance, support, and technical input, and to Dr. Benjamin Klein for his support and technical guidance regarding device simulation. Thanks also to Rick Brown for the technical advice and the welcome distractions. Those educators who were instrumental in my development as a student and as a person, in particular Ms. Sheila Smith and Mr. Scott Merrell, taught me to ask questions and to seek answers, and have had a lasting impact on my thought processes. Thanks to both of you. I am deeply grateful to my family – my parents and my sister, Kelly – for their love and support. Finally, I would like to thank my wife, Jaime, for her unwavering love and support in finishing this work. TABLE OF CONTENTS LIST OF TABLES .........................................................................................................x LIST OF FIGURES..................................................................................................... xi LIST OF SYMBOLS AND ABBREVIATIONS........................................................xvi SUMMARY ...............................................................................................................xviii CHAPTER 1: INTRODUCTION.............................................................................1 1.1 STATE OF THE ART IN SOLID STATE LIGHTING ............................................................1 1.1.1 Semiconductor Materials for SSL................................................................................2 1.1.2 GaN Growth Technology............................................................................................7 1.1.3 Design and Fabrication of GaN-based Emitters......................................................8 1.1.4 Current Challenges facing SSL ..................................................................................10 1.1.4.1 Efficacy and Efficiency......................................................................................10 1.1.4.2 Thermal Management........................................................................................11 1.1.4.3 Color.....................................................................................................................12 1.1.4.4 Cost.......................................................................................................................13 1.2 ALTERNATIVE SUBSTRATES ............................................................................................15 1.3 RESEARCH OBJECTIVES ...................................................................................................17 1.4 CONTRIBUTIONS ...............................................................................................................17 1.5 MATERIAL PROPERTIES ...................................................................................................18 1.5 SUMMARY ...........................................................................................................................18 CHAPTER 2: BACKGROUND .................................................................................. 21 2.1 SI AS A SUBSTRATE FOR GAN EPITAXY .........................................................................21 2.1.1 Advantages of Silicon as a Substrate.........................................................................21 2.1.2 Challenges for GaN growth on Silicon....................................................................22 2.1.3 Literature Review.........................................................................................................24 2.2 ZNO AS A SUBSTRATE FOR GAN EPITAXY ...................................................................34 2.2.1 Advantages of ZnO as a Substrate............................................................................34 2.2.2 Challenges for GaN Growth on ZnO......................................................................36 2.2.3 Literature Review.........................................................................................................36 2.3 SUMMARY ...........................................................................................................................39 CHAPTER 3: EXPERIMENTAL EQUIPMENT AND TECHNIQUES ............40 3.1 MODELING ........................................................................................................................40 3.2 GROWTH ............................................................................................................................40 3.2.1 MOCVD Growth........................................................................................................41 3.2.1.1 Thermodynamics................................................................................................41 3.2.1.2 Kinetics ................................................................................................................43 3.2.1.3 Fluid Dynamics and Mass Transport ..............................................................46 3.2.1.4 MOCVD Growth of GaN................................................................................48 3.2.2 ALD Growth................................................................................................................54 3.3 CHARACTERIZATION .......................................................................................................55 3.3.1 Structural Characterization.........................................................................................55 3.3.1.1 X-ray Diffraction (XRD)...................................................................................56 3.3.1.2 X-ray Reflectivity (XRR) ...................................................................................58 vi 3.3.1.3 Raman Spectroscopy..........................................................................................59 3.3.2 Surface Characterization.............................................................................................61 3.3.2.1 Atomic Force Microscopy (AFM) ...................................................................62 3.3.2.2 Scanning Electron Microscopy (SEM)............................................................63 3.3.2.3 Transmission Electron Microscopy (TEM)....................................................63 3.3.3 Optical Characterization.............................................................................................64 3.3.3.1 Photoluminescence Spectroscopy (PL)...........................................................64 3.3.3.2 Optical Transmission.........................................................................................65 3.3.4 Electrical Characterization .........................................................................................66 3.3.4.1 Hall Effect Measurement ..................................................................................66 3.3.4.2 Secondary Ion Mass Spectrometry (SIMS).....................................................67 3.3.5 Device Characterization..............................................................................................69 3.3.5.1 Current-Voltage (I-V) Measurement ...............................................................69 3.3.5.2 Electroluminescence (EL).................................................................................70 3.3.5.3 Optical Power Measurements...........................................................................71 3.4 DEVICE PROCESSING .......................................................................................................71