Mechanism of Heteroepitaxial Growth of Boron Carbide on the Si-Face of 4H-SiC

TL;DR

This study investigates the complex early growth stages of heteroepitaxial boron carbide on 4H-SiC, revealing phase formation and solid-state diffusion effects that influence the epitaxial growth process.

Contribution

It provides detailed insights into the reactions and phase evolution during boron carbide heteroepitaxy on SiC, highlighting the effects of temperature ramp-up and diffusion.

Findings

Formation of amorphous B-containing layer after boridation

Presence of Si, SiB6 phases due to solid-state diffusion

Epitaxial BxC layers with [1010] orientation and B4C composition

Abstract

Heteroepitaxial boron carbide (BxC) can be grown on Si face 4H-SiC(0001) using a two-step process involving substrate boridation at 1200$^\circ$C under BCl3 + H2 followed by a chemical vapor deposition (CVD) growth step at 1600$^\circ$C by adding C3H8 precursor. However, in-depth investigation of the early growth stages revealed that complex reactions occur before starting the CVD at high temperature. Indeed, after boridation, the 35 nm BxC buffer layer is covered by an amorphous B-containing layer which evolves and reacts during the temperature ramp up between 1200 to 1600$^\circ$C. Despite the formation of new phases (Si, SiB6), which could be explained by significant solid-state diffusion of Si, C and B elements through the thin BxC layer, the CVD epitaxial re-growth upon reaching 1600$^\circ$C does not seems to be affected by these phases. The resulting single crystalline BxC layers display the epitaxial relationships [1010]BxC(0001)||[1010]4H-SiC(0001). The layers exhibit a B4C composition, e.g. the highest possible C content for the BxC solid solution.