“…Others have investigated the incorporation efficiency of Si into GaAs as a function of precursors used, substrate miscut, and temperature. 27,28 Using silane (SiH 4 ) as the silicon precursor, the ratio of the solid composition X sol ϵ͓Si͔/͓Ga͔ to the gas-phase composition X gas ϵ͓SiH 4 ͔/͓TMGa͔ has been found to be 0.1 for gas-phase compositions up to 5ϫ10 Ϫ2 , 27 when TBAs is used as the arsenic source. The use of disilane (Si 2 H 6 ) as the Si precursor is generally found to have at least as high an incorporation efficiency as silane, per silicon atom, 29 so we estimate the ratio of X sol to X gas ϵ͓Si 2 H 6 ͔/͓TMGa͔ in our case to be 0.2.…”