Low‐Pressure Chemical Vapor Deposition of Hexagonal Boron Nitride on a‐Plane Sapphire Using BCl₃ as a Boron Source

Abstract

Hexagonal boron nitride (h‐BN) thin films are grown on a‐plane sapphire substrates at different temperatures, Tg, by low‐pressure chemical vapor deposition with BCl3 and NH3 as boron and nitrogen sources, respectively, and their crystallographic and luminescence properties are compared with those grown on c‐plane sapphire. A notable difference from the c‐plane sapphire is that the substrate surface is significantly nitrided during film growth at Tg higher than 1200 °C, whereas no such nitridation is observed up to 1500 °C for the growth on c‐plane sapphire. The nitridation of the substrate surface is found to cause the degradation of the film quality. However, the properties of the films grown on a‐plane sapphire at Tg lower than 1200 °C are comparable to or better than those grown on c‐plane sapphire. The h‐BN epitaxial film is grown at 1150 °C epitaxially on the a‐plane sapphire substrate with the out‐of‐plane and in‐plane relationships, h‐BN//sapphire andh‐BN//sapphire, respectively. This study suggests that a‐plane sapphire is suitable for growing high‐quality h‐BN films at relatively low Tg.