Controlling GaN Morphology on Si(111) by Al Pre‑Deposition and Ga/N Ratio in MBE
Abstract
By tuning the Ga/N ratio and introducing a brief Al pre‑deposition, we achieved precise control over GaN growth modes—nanocolumns, nanowall networks, and compact films—on Si(111) via plasma‑assisted molecular beam epitaxy (PA‑MBE). GaN nanocolumns emerged under N‑rich conditions on bare Si, while a higher Ga flux produced a dense compact film. Remarkably, a 40‑second Al pre‑deposition before GaN growth yielded a continuous in‑plane nanowall network. Atomic force microscopy revealed that Al forms ~80 nm droplets (~6.7 nm tall). We propose a growth model wherein GaN nucleates on bare Si, but growth is suppressed above Al droplets, leading to the characteristic network. This approach eliminates obstacles in nano‑device fabrication and demonstrates a scalable route to high‑quality GaN nanostructures on silicon.
Nanomaterials
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