Huang C.-H.; Chou Y.-C.YI-CHIA CHOU2022-06-302022-06-30202025740970https://www.scopus.com/inward/record.uri?eid=2-s2.0-85094673038&doi=10.1021%2facsanm.0c01658&partnerID=40&md5=205d618bbef398a38795e6d54426f9a8https://scholars.lib.ntu.edu.tw/handle/123456789/614657We introduce a pit-formation method on a GaN substrate to obtain ultra-long GaN nanorods (NRs) grown homoepitaxially through hydride vapor phase epitaxy (HVPE) without an additional catalyst or a complex lithography procedure. The pits were created by annealing and nitridation at a high temperature on the GaN substrate; thus, GaN NRs were pinned at the pits during growth processes. The nucleation barrier of the GaN NR can be lowered by creating pits on the GaN substrate, leading to a higher possibility of triggering NR growth at a higher growth temperature. The conditions of the growth temperature were found to critically influence the NR aspect ratio and height. The GaN NRs with c-orientation achieves an ∼11.2 μm height in average in 20 min where the maximum height reaches 12.7 μm. The possible diffusion pathway of Ga adatoms was also discussed to reach the maximum height of a GaN NR at various growth temperatures. In addition, room-temperature cathodoluminescence measurements on the GaN NRs show a GaN-related near band gap emission peak and the luminescence intensity is even better than that of the GaN substrate. Such ultra-long GaN nanorods with the optical properties can be evaluated for sensing materials. Copyright © 2020 American Chemical Society.Aluminum nitride; Aspect ratio; Cathodoluminescence; Crystallization; Energy gap; Growth temperature; III-V semiconductors; Nanorods; Nucleation; Optical properties; Band-gap emission; Diffusion pathways; High temperature; Hydride vapor phase epitaxy; Luminescence intensity; Nucleation barrier; Nucleation energy; Sensing material; Gallium nitride[SDGs]SDG7journal article10.1021/acsanm.0c016582-s2.0-85094673038