Hexagonal boron nitride film on sapphire substrate grown by low-pressure and high-temperature halide vapor phase epitaxy

Abstract

(002) hexagonal boron nitride (h-BN) films are epitaxially grown on c-plane sapphire substrates by low-pressure and high-temperature halide vapor phase epitaxy, using boron trichloride and ammonia as the boron source and nitrogen source. The influence of the gas phase composition has been investigated to improve the crystalline quality. For the deposition at a temperature of 1650 °C, the optimal nitrogen to boron ratio is identified as 6 and the corresponding deposition rate is around 26 nm/min. Under this condition, the c-lattice parameter of the h-BN layer is 6.66 Å. The h-BN film exhibits high transmittance larger than 70% in the visible range and its optical bandgap is determined to be 5.2 eV.