Metalorganic molecular etching: A new technology in molecular beam epitaxy
In vapor phase epitaxy (VPE) technology, substitute compounds had to be developed in lieu of the extremely flammable silicon source used which is silane (SiH4). Thus the compounds dichlorosilane (SiH2Cl2), trichlorosilane (SiHCl3) and silicon tetrachloride (SiCl4) came to be used. Of these, SiCl4 is known to have served the original purpose because this compound is a non-flammable liquid. It became apparent also that the introduction of chlorine containing compounds improves growth yielding epitaxial layers instead of amorphous silicon. The secret was back etching, the re-formation of Si-Cl compounds, that slows down the growth process thereby enabling the control of growth as a layer by layer process.