TY - JOUR
T1 - Influence of TMAl preflow on AlN epitaxy on sapphire
AU - Sun, Haiding
AU - Wu, Feng
AU - Park, Young Jae
AU - Al tahtamouni, T. M.
AU - Li, Kuang-Hui
AU - Alfaraj, Nasir
AU - Detchprohm, Theeradetch
AU - Dupuis, Russell D.
AU - Li, Xiaohang
N1 - KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: The KAUST authors would like to acknowledge the support of GCC Research Program REP/1/3189-01-01, Baseline BAS/1/1664-01-01, and Equipment BAS/1/1664-01-07. The work at QU was supported by GCC Research Program GCC-2017–007. The work at Georgia Institute of Technology was supported in part by DARPA under Grant No. W911NF-15-1-0026 and NSF under Grant No. DMR-1410874. R.D.D. acknowledges the additional support of the Steve W. Chaddick Endowed Chair in Electro-Optics and Georgia Research Alliance.
PY - 2017/5/12
Y1 - 2017/5/12
N2 - The trimethylaluminum (TMAl) preflow process has been widely applied on sapphire substrates prior to growing Al-polar AlN films by metalorganic chemical vapor deposition. However, it has been unclear how the TMAl preflow process really works. In this letter, we reported on carbon's significance in the polarity and growth mode of AlN films due to the TMAl preflow. Without the preflow, no trace of carbon was found at the AlN/sapphire interface and the films possessed mixed Al- and N-polarity. With the 5 s preflow, carbon started to precipitate due to the decomposition of TMAl, forming scattered carbon-rich clusters which were graphitic carbon. It was discovered that the carbon attracted surrounding oxygen impurity atoms and consequently suppressed the formation of AlxOyNz and thus N-polarity. With the 40 s preflow, the significant presence of carbon clusters at the AlN/sapphire interface was observed. While still attracting oxygen and preventing the N-polarity, the carbon clusters served as randomly distributed masks to further induce a 3D growth mode for the AlN growth. The corresponding epitaxial growth mode change is discussed.
AB - The trimethylaluminum (TMAl) preflow process has been widely applied on sapphire substrates prior to growing Al-polar AlN films by metalorganic chemical vapor deposition. However, it has been unclear how the TMAl preflow process really works. In this letter, we reported on carbon's significance in the polarity and growth mode of AlN films due to the TMAl preflow. Without the preflow, no trace of carbon was found at the AlN/sapphire interface and the films possessed mixed Al- and N-polarity. With the 5 s preflow, carbon started to precipitate due to the decomposition of TMAl, forming scattered carbon-rich clusters which were graphitic carbon. It was discovered that the carbon attracted surrounding oxygen impurity atoms and consequently suppressed the formation of AlxOyNz and thus N-polarity. With the 40 s preflow, the significant presence of carbon clusters at the AlN/sapphire interface was observed. While still attracting oxygen and preventing the N-polarity, the carbon clusters served as randomly distributed masks to further induce a 3D growth mode for the AlN growth. The corresponding epitaxial growth mode change is discussed.
UR - http://hdl.handle.net/10754/623481
UR - http://aip.scitation.org/doi/10.1063/1.4983388
UR - http://www.scopus.com/inward/record.url?scp=85019134716&partnerID=8YFLogxK
U2 - 10.1063/1.4983388
DO - 10.1063/1.4983388
M3 - Article
SN - 0003-6951
VL - 110
SP - 192106
JO - Applied Physics Letters
JF - Applied Physics Letters
IS - 19
ER -