Reduction in Residual Impurities in Chemical Vapor Deposition–Grown Hexagonal Boron Nitride Thin Films

Abstract

The residual impurities in chemical vapor deposition (CVD)‐grown hexagonal boron nitride (h‐BN) on Al2O3 substrate grown by CVD using BN‐molded susceptor with B2H6 as a boron precursor are investigated. The Si, C, and O residual impurities of 2.6 × 1016, 3.4 × 1018, and 2.0 × 1017 cm−3 are achieved. These concentrations are two orders of magnitude lower than those when grown on the SiC‐coated graphite susceptor using trimethylboron (TMB) and the lowest values in the CVD‐grown h‐BN thin films. The cathodoluminescence spectrum has 5.5 eV as a broad peak and 4 eV as several peaks. The free excitonic recombination at the higher energy emission (5.79 eV) is owing to the reduction in residual impurities. The absorption coefficient of 1 × 104 cm−1 is observed in the energy range below 5 eV only when using the SiC‐coated graphite susceptor, which is most probably associated with Si contamination in the BN layer. The negligible absorption coefficient when using the BN‐molded susceptor presents high‐purity h‐BN signature.