Growth mechanism of AlN on hexagonal BN/sapphire substrate by metal-organic chemical vapor deposition

The growth mechanism of AlN materials on a sapphire substrate with a hexagonal BN overlayer (hBN/sapphire) by metal-organic chemical vapor deposition (MOCVD) is reported for the first time. Here, we have grown high-quality AlN films on sapphire with a hBN layer by MOCVD. A growth model has been proposed to clarify the growth mechanism of AlN on hBN. To facilitate the nucleation of AlN on hBN/sapphire, we have introduced some artificial dangling bonds for hBN through O-2 plasma treatment (hBN-O-2). The change in atom connective structure of hBN materials after the treatment has been inferred according to the results of Raman spectroscopy and X-ray photoelectron spectroscopy. The total dislocation density of AlN on hBN-O-2/sapphire is much lower than that of AlN on hBN/sapphire, which has evidenced the high crystalline quality of epitaxial films and the effect of the O-2 treatment. Moreover, an AlGaN-based deep-ultraviolet light emitting diode (DUV LED) structure on hBN-O-2/sapphire was achieved. The electroluminescence results have exhibited strong emissions with a peak wavelength of 290 nm, which further confirms the high quality of the AlN. This work provides a possible solution for further developing efficient DUV LEDs on 2D materials as well as other unconventional substrates.