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.

Phase Evolution of Boron Nitride and Carbide during Chemical Vapor Deposition

“…ere are a variety of options regarding boron precursors that can be used for BN growth, each with its benefits and drawbacks. From the alternative boron precursors used in recent literature, diborane (B2H6) [79][80][81][82][83] is the most used boron hydride while BCl3 [84][85][86][87][88] is a common boron halide. Boron hydrides benefit from having hydrogen as a by-product but are oen considered dangerous if not handled properly due to their explosive and poisonous nature.…”

The Influence of Carbon on Polytype and Growth Stability of Epitaxial Hexagonal Boron Nitride Films

“…Boron precursors include boron hydrides, like diborane (B 2 H 6 ), [21][22][23] or organoboranes, like triethylborane B(C 2 H 5 ) 3 (TEB), [24,25] and trimethylborane B(CH 3 ) 3 (TMB). [18,26] Numerous reports in the literature [16,27,28] show that temperatures ≈1500 °C are required for epitaxial growth of h-BN and r-BN thin films, that exceed a few monolayers, limiting the substrates that can be used in thermal CVD. Sapphire (Al 2 O 3 ) [22,[29][30][31] and silicon carbide (SiC) [19,32,33] are the two most common substrates.…”