Polarity Effect on the Heteroepitaxial Growth of BxC on 4H-SiC by CVD

TL;DR

This study investigates how substrate polarity influences the heteroepitaxial growth of boron carbide on 4H-SiC using CVD, revealing that surface treatment and polarity significantly affect film quality and orientation.

Contribution

It demonstrates that substrate polarity and pre-treatment steps can control the heteroepitaxial growth of BxC on 4H-SiC, providing insights into nucleation mechanisms.

Findings

Heteroepitaxial growth occurs on C face with high C/B ratios.

Pre-treatment with boridation enables heteroepitaxy on both polarities.

Surface chemistry influences nucleation and film orientation.

Abstract

The chemical vapor deposition (CVD) growth of boron carbide (B x C) layers on 4H-SiC, 4{\textdegree}off substrates was studied. Depending on the polarity of the substrate, different results were obtained. On Si face, the direct CVD growth at 1600{\textdegree}C under a mixture of BCl 3 +C 3 H 8 systematically led to polycrystalline B x C films, whatever the C/B ratio in the gas phase. On the C face, heteroepitaxial growth was obtained for C/B ratios = 12 or higher with a step bunched morphology. If a boridation step (10 min at 1200{\textdegree}C under BCl 3 flow) was used before the CVD growth, then heteroepitaxy was successful on both substrate polarities. To explain these results, a mechanism is proposed which involves the nature of the chemical bonds at the early stage of nucleation. It is suggested that a full B coverage of the SiC surface should favor the nucleation of the B-rich (0001) plane of B x C, promoting thus the heteroepitaxial growth along this direction.