Challenges in Carrier Gas-Controlled Growth of GaN Nanorods: Achieving Uniformity and Top-Facet Tunability in Pulsed-Mode MOCVD

Driven by the proliferation of nanoscale optoelectronic devices, achieving precise control over the growth of GaN nanorods (NRs) has become increasingly important. Selective area growth (SAG) using the pulsed-mode technique has demonstrated promising results in its ability to produce NRs with the desired dimensions and surface morphology. However, addressing the issue of growth nonuniformity, a previously overlooked aspect, remains a critical challenge. In this study, we leverage a commercial metal–organic chemical vapor deposition system to investigate the impact of using a pulsed-mode approach. We shed light on the pivotal role of carrier gases in the growth mechanism and elucidate their interplay with other parameters. We discuss the growth uniformity and the possible challenges associated with ambient conditions, which can cause undesirable edge effects or rod-to-rod inhomogeneities. Furthermore, we demonstrate the ability to tailor NR morphologies by simply manipulating the carrier gas. Our analysis, grounded in the kinetic Wulff plot, is compared with the existing literature to validate our model. Additionally, the optical properties of both GaN NR morphologies are examined upon growing InGaN/GaN shells, revealing emission tunability. Our work exposes some of the often-overlooked aspects of SAG NRs and contributes to a better understanding of the pulsed-mode growth mechanism.