Patent ID: 8545627

Claim:
A method for forming an epitaxial buffer layer over a substrate by molecular beam epitaxy comprising: contacting a substrate with a precursor gas at a temperature and a pressure suitable for depositing an epitaxial buffer layer over the substrate; the epitaxial buffer layer having a thickness of greater than 100 nm and comprising ZrB 2 , AlB 2 , HfB 2 , Hf x Zr 1-x B 2 , Hf x Al 1-x B 2 , Zr x Al 1-x B 2 , or Zr z Hf y Al 1-z-y B 2 wherein the sum of z and y is less than or equal to 1; wherein the precursor gas comprises (i) greater than 95% v/v hydrogen gas and (ii) 0.1-5% v/v of a precursor source, wherein the precursor source comprises Zr(BH 4 ) 4 , Hf(BH 4 ) 4 , an Al source, or mixtures thereof; and wherein the use of the hydrogen gas reduces the surface roughness of the epitaxial layer by acting as a diluent to prevent the poisoning of the surface of the epitaxial layer with B-rich fragments.