Density-Controlled Self-Assembled Dodecagonal GaN Nanorods Grown on Plasma-Treated Sapphire for All-in-One Multicolor Emission

Abstract

This study explores a novel method for the growth of self-assembled GaN nanorods (NRs) on sapphire substrates using metal–organic chemical vapor deposition, leveraging plasma treatment to simplify the process and eliminate the need for a separate nucleation step. Oxygen plasma treatment modifies the sapphire surface, introducing nanoscale features and enhancing its chemical reactivity. These surface changes directly influence the nucleation process, resulting in a systematic increase in NR density (up to ∼10 ⁸ cm ^–2) and a reduction in size with prolonged treatment durations. Interestingly, the NRs exhibit a distinct dodecagonal morphology, which is linked to the altered epitaxial relationship between GaN and the treated sapphire substrate. To demonstrate the applicability of this method, InGaN/GaN multiple quantum wells were successfully regrown on the NRs, enabling precise control of emission wavelengths from violet to green. This streamlined approach not only offers a reliable pathway for tuning optical properties but also facilitates the simultaneous growth of multiwavelength-emitting devices on a single substrate. The findings highlight the potential of this technique for scalable, cost-effective fabrication of flexible optoelectronic devices, opening new possibilities in multicolor light-emitting diode technologies.