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Title: Influences of group-III source preflow on the polarity, optical, and structural properties of GaN grown on nitridated sapphire substrates by metal-organic chemical vapor deposition

We report the influences of group-III source preflow, which were introduced prior to the growth of the low temperature GaN on the polarity, photoluminescence (PL), and crystallographic properties of GaN epilayers grown on nitridated c-plane sapphire substrates by metal-organic chemical vapor deposition. By studying the surface morphology evolutions under chemical etching in KOH, we found that with increasing the trimethyl-gallium (TMGa) preflow duration (t), the polarity of the GaN film can be changed from a complete N-polarity to a mixture of N- and Ga-polarity and further to a complete Ga-polarity. PL and high-resolution X-ray diffraction studies revealed that the impurity incorporation and the edge- and screw-type threading dislocations are strongly polarity dependent. A further study at the optimized t (i.e., 30 s for TMGa) shows that the polarity inversion of GaN can be realized not only by TMGa preflow but also by trimethyl-aluminium preflow and by trimethyl-indium preflow. A two-monolayer model was employed to explain the polarity inversion mechanism.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4]
  1. Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore)
  2. Institute of Materials Research and Engineering (IMRE), A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)
  3. (IMRE), A*STAR (Agency for Science, Technology and Research), 3 Research Link, Singapore 117602 (Singapore)
  4. (Singapore)
Publication Date:
OSTI Identifier:
22399356
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 12; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ALUMINIUM; CHEMICAL VAPOR DEPOSITION; CRYSTAL GROWTH; DISLOCATIONS; GALLIUM; GALLIUM NITRIDES; INDIUM; MORPHOLOGY; ORGANOMETALLIC COMPOUNDS; PHOTOLUMINESCENCE; POTASSIUM HYDROXIDES; SAPPHIRE; SUBSTRATES; THIN FILMS; X-RAY DIFFRACTION