In this study, we investigate the effect of Al/N source ratios and growth rates on the growth and structural properties of AlN films on c-plane sapphires by plasma-assisted molecular beam epitaxy. Both growth rates and Al/N ratios affect crystal qualities of AlN films. The full width at half maximum (FWHM) values of (1015) X-ray rocking curves (XRCs) change from 0.22 to 0.31° with changing of the Al/N ratios, but the curves of (0002) XRCs change from 0.04 to 0.45° with changing of the Al/N ratios. This means that structural deformation due to dislocations is slightly affected by the Al/N ratio in the (1015) XRCs but affected strongly for the (0002) XRCs. From the viewpoint of growth rate, the AlN films with high growth rate (HGR) show better crystal quality than the low growth rate (LGR) films overall, as shown by the FWHM values of the (0002) and (1015) XRCs. Based on cross-sectional transmission electron microscope observation, the HGR sample with an Al/N ratio of 3.1 shows more edge dislocations than there are screw and mixed dislocations in the LGR sample with Al/N ratio of 3.5.

Abstract
1. Introduction
2. Experimental
3. Results and Discussion
4. Conclusions
References

• Se Hwan Lim(Graduate School of Energy Science and Technology, Chungnam National University)
• Eun-Jung Shin(Graduate School of Energy Science and Technology, Chungnam National University)
• Hyo Sung Lee(Department of Materials Science and Engineering, Chungnam National University)
• Seok Kyu Han(Department of Materials Science and Engineering, Chungnam National University)
• Duc Duy Le(Department of Materials Science and Engineering, Chungnam National University)
• Soon-Ku Hong(Department of Materials Science and Engineering, Chungnam National University) Corresponding author