Self-assembled growth of inclined GaN nanorods on (10−10) m-plane sapphire using metal–organic chemical vapor deposition

• Inclined and highly ordered GaN nanorods were grown on m-sapphire by MOCVD.
• The growth of GaN nanorods on m-sapphire was very sensitive to the growth parameters.
• The epitaxial relationship between GaN nanorods and m-sapphire was investigated.
• Cathodoluminescence revealed the characteristics of the highly Si-doped GaN nanorods.

We report the self-assembled growth of inclined and highly ordered GaN nanorods on (10−10) m-plane sapphire by metal–organic chemical vapor deposition, without metal catalyst. To determine the growth mechanism we performed a systematic study of the effect of the SiH4 flow, V/III ratio, growth temperature and growth time on growth behavior, demonstrating that optimized parameters were required for the growth of nanorods with high aspect ratios. High resolution X-ray diffraction showed that the nanorods were inclined at an angle of 58.4° with respect to the substrate normal and followed a well-defined epitaxial relationship with respect to the on-axis plane of the nanorods, the (11–22) semipolar plane, and the (10−10) m-plane sapphire. Finally cathodoluminescence showed that the near band edge emission of the Si-doped nanorod was asymmetric and broad owing to the band filling effect resulting from high carrier concentration, compared to the undoped GaN.