Achieving smooth and transferable AlN films on h-BN via in-situ dual-step preflow treatment

Abstract Aluminum nitride (AlN) epitaxy was performed on multilayer hexagonal boron nitride (h-BN) via metalorganic vapor deposition (MOCVD) under varying in‑situ preflow conditions. A dual‑step preflow strategy—sequential NH 3 followed by TMAl—was developed to obtain mechanically transferable AlN films with smooth morphology and single-crystalline quality. Contrast experiments suggest that the NH 3 step enhances nucleation density, while the subsequent TMAl step suppresses mixed polarity in early growth. This fully in‑situ process replaces conventional ex‑situ surface modifications of h-BN, offering improved reproducibility and MOCVD compatibility, and benefiting the integration of transferable AlN‑based heterostructures into deep‑UV optoelectronic and high‑power electronic devices.