title: Inclined angle-controlled growth of GaN nanorods on m-sapphire by metal organic chemical vapor deposition without a catalyst.
abstract: In this study, we have intentionally grown novel types of (11-22)- and (1-10-3)-oriented(3) and self-assembled inclined GaN nanorods (NRs) on (10-10) m-sapphire substrates using metal organic chemical vapor deposition without catalysts and ex situ patterning. Nitridation of the m-sapphire surface was observed to be crucial to the inclined angle as well as the growth direction of the GaN NRs. Polarity-selective KOH etching confirmed that both (11-22) and (1-10-3) GaN NRs are nitrogen-polar. Using pole figure measurements and selective area electron diffraction patterns, the epitaxial relationship between the inclined (11-22) and (1-10-3) GaN NRs and m-sapphire substrates was systematically demonstrated. Furthermore, it was verified that the GaN NRs were single-crystalline wurtzite structures. We observed that stacking fault-related defects were generated during the initial growth stage using high-resolution transmission electron microscopy. The blue-shift of the near band edge (NBE) peak in the inclined angle-controlled GaN NRs can be explained by a band filling effect through carrier saturation of the conduction band, resulting from a high Si-doping concentration; in addition, the decay time of NBE emission in (11-22)- and (1-10-3)-oriented NRs was much shorter than that of stacking fault-related emission. These results suggest that defect-free inclined GaN NRs can be grown on m-sapphire without ex situ treatment.
authors.affiliation: Convergence Center for Advanced Nano Semiconductor (CANS), Department of Nano-Optical Engineering, Korea Polytechnic University (KPU), Siheung 429-793, Korea.
authors.forename: Kyuseung
authors.initials: K
authors.lastname: Lee
authors.forename: Sooryong
authors.initials: S
authors.lastname: Chae
authors.forename: Jongjin
authors.initials: J
authors.lastname: Jang
authors.forename: Daehong
authors.initials: D
authors.lastname: Min
authors.forename: Jaehwan
authors.initials: J
authors.lastname: Kim
authors.forename: Daeyong
authors.initials: D
authors.lastname: Eom
authors.forename: Yang-Seok
authors.initials: YS
authors.lastname: Yoo
authors.forename: Yong-Hoon
authors.initials: YH
authors.lastname: Cho
authors.forename: Okhyun
authors.initials: O
authors.lastname: Nam