ABSTRACT
A direct band gap that covers the entire optical spectrum from <1 to >6 eV, a high saturation velocity, and high breakdown ˆeld strength makes GaN and its alloys with AlN and InN, hereafter referred to as III-nitrides, of importance for optoelectronic and high-power and/or high-frequency electronic applications. Following some earlier work and asacontinuation of research on group III-A (Ga, Al, and In) phosphides and arsenides, GaN was ˆrst shown to have a direct band gap of 3.39 eV in 1969 by Maruska and Tietjen at RCA laboratories (Maruska and Tietjen 1969). However, lack of native substrates for epitaxial growth, such as for GaAs and Si, hampered further progress until 1986, when Amano and Akasaki reported growth of uniform layers on c-plane sapphire using low-temperature (LT) (∼600°C) AlN buffer layers by organometallic vapor phase epitaxy (OMVPE) (Amano et al. 1986). Further research by Amano and Akasaki and by Nakamura between 1989 and 1995 ˆrmly established sapphire
CONTENTS
5.1 Introduction, Historical Perspective, and Current Status .................... 209 5.2 Interfaces and Epitaxial Relationships.................................................... 212 5.3Defects in III-Nitride Layers ..................................................................... 215 5.4In Situ Monitoring for Stress and Microstructural Evolution ............. 218 5.5 Growth of AlN on (111) Si ......................................................................... 221 5.6 Growth of GaN on (111) Si Using AlN Buffer Layers ........................... 229 5.7 Growth of AlGaN Buffer Layers ..............................................................235 5.8Growth of GaN on Graded AlGaN Buffer Layers ................................238 5.9Growth of GaN Using AlN Interlayers ................................................... 240 5.10 Dislocations and Compressive Stress Reduction in GaN Layers ........ 246 Acknowledgments .............................................................................................. 249 References .............................................................................................................250
