Journal
COATINGS
Volume 11, Issue 8, Pages -Publisher
MDPI
DOI: 10.3390/coatings11080956
Keywords
AlN; sapphire; radio frequency sputtering; face-to-face annealing; crystallinity; X-ray diffraction; atomic force microscopy; deep-ultraviolet light-emitting diodes
Categories
Funding
- Ministry of Education, Culture, Sports, Science, and Technology under the Program for Building Regional Innovation Ecosystems
- JSPS KAKENHI [JP16H06415, JP19K15025, JP21K04903, JP21K14545]
- JST CREST [16815710]
- JST aXis [JPMJAS2011]
- Ministry of Economy, Trade and Industry Monozukuri R&D Support Grant Program [JPJ005698]
- NEDO leading research program
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In this study, AlN films were deposited on sapphire substrates by sputtering deposition followed by high-temperature annealing. The research found that reducing the amount of Ar in the sputtering gas and decreasing the chamber pressure can significantly improve the crystallinity of the annealed AlN films.
Face-to-face annealed sputter-deposited aluminum nitride (AlN) templates (FFA Sp-AlN) are a promising material for application in deep-ultraviolet light-emitting diodes (DUV-LEDs), whose performance is directly related to the crystallinity of the AlN film. However, the influence of the sputtering conditions and annealing on the crystallinity of AlN films have not yet been comprehensively studied. Accordingly, in this study, we fabricate AlN films on sapphire substrates through sputtering deposition followed by face-to-face high-temperature annealing, and investigate the influence of the sputtering conditions, such as the sputtering gas species and chamber pressure, on the crystallinity of the AlN films before and after annealing. The results revealed that reducing the amount of Ar in the sputtering gas significantly enhances the c-axis oriented growth during the initial stages of sputtering deposition and mitigates the tilt disorder of the layer deposited on the initial layer, resulting in low threading dislocation densities (TDDs) in the annealed AlN films. Decreasing the chamber pressure also effectively improves the crystallinity of the annealed AlN films. Thus, although high-temperature annealing can reduce the TDDs in AlN films, the properties of the as-sputtered AlN films have a significant effect on the crystallinity of FFA Sp-AlN films.
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