Influence of sapphire substrate with miscut angles on hexagonal boron nitride films grown by halide vapor phase epitaxy

Abstract

(002) hexagonal boron nitride (h-BN) micron films were epitaxially grown on c-plane sapphire substrates with miscut angles to m-plane (m-miscut angle) by high-temperature and low-pressure halide vapor phase epitaxy. Herein, the influence of sapphire substrate with m-miscut angles, ranging from 0.1° to 1°, on the morphology, crystal quality, and residual stress of BN micron films was thoroughly investigated. XRD result demonstrated that the as-grown BN films were predominantly [002]-oriented h-BN with t-BN phase. The growth rate of h-BN remained unchanged at about 62 nm min⁻¹ regardless of the substrate miscut angle, while the h-BN (002) diffraction peak broadened and the E_2g vibration mode of h-BN exhibited a blueshift as the miscut angle increases. With an m-miscut angle of 0.1°, the crystal quality of the BN film was most optimized and the content of h-BN reached 45.93% at the growth temperature of 1650 °C and V/III ratio of 6. The residual stress was also most released, in which the peak position and full width at the half maximum of E_2g peak for h-BN were 1368 cm⁻¹ and 34 cm⁻¹, respectively. Under this condition, h-BN grows in a layered form and the nuclei coalesce into smooth micron-sized grains at the surface. The stoichiometric ratio between nitrogen and boron in the h-BN films is less than 1, possibly due to nitrogen deficiency caused by ammonia pulse growth mode.