Ke Xu

Dr. Ke Xu, professor and director of nano-characterization lab in Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, who founded Suzhou Nanowin Science and Technology Co. Ltd. and acts as president. Dr. Xu has devoted to III-nitride semiconductors for about 20 years, for growth of high quality materials by MOCVD, MBE and HVPE, as well as the effects of polarity on material growth. He first revealed the unique effects of the film polarity on InN epitaxial growth. He and his team have successfully demonstrated mass production of 2~4 inch bulk GaN substrate growth by HVPE. He also developed characterization technology and instruments based on scanning tunneling microscopy for studying physics of single defect and investigating novel physics in III-nitride based quantum structures. He has published more than 80 peer reviewed papers and pended 50 patents, delivered 20 invited talks in international conference. He won Qiushi Outstanding Youth Award-“technology transformation awards” in 2010, and Suzhou Mayer Awards in 2011, and “The outstanding pioneer for combination research and industrialization” sponsored by Chinese Association for Science and Technology in 2012,  and won China National Funds for Distinguished Young Scientists in 2013.  He now also serves as committee member of national high-tech program, member of national nano-technology standardization committee, senior fellow of Chinese Institute of electronics, member of branch of optical materials in optical society.
Abstract .......

   Substrates for GaN epitxial growth were reviewed, and future developing trends for nitride industry were discussed in this talk.
We reported 2~4-inch bulk GaN growth by Hydride Vapor Phase Epitaxy (HVPE). Sapphire substrate was used as the starting substrate. An optical reflectance system was assembled in the HVPE system, which can detect the in-situ reflectivity and the stress of the epilayer simultaneously. By fabricating different nano-structure on the surface of the starting substrate, strain distribution can be modulated in the following thick GaN layer grown by HVPE. Fluid dynamics and growth kinetics were theoretically simulated, the stress and dislocation evolution in HVPE growth of GaN was characterized by confocal micro-Raman spectroscopy, high resolution XRD, cathodoluminescence, TEM, and in-situ optical monitoring, providing unambiguous understandings in critical issues of GaN substrate fabrication by HVPE.
  The FWHMs of x-ray rocking curve of GaN (002) and (102) reflection were both about 30~40arcsec, dislocation etching pits density is in 104cm-2 order. The un-doped bulk GaN has background electron concentration in the order of 1016cm-3, and electron mobility of around 1400V·s/cm2.
  In the presentation, we will also review other growth methods for bulk GaN, such as Na-flux method, ammonothermal method, for bulk GaN growth. Homoepitaxial growth of GaN was also discussed.