Doping to B concentrations of more than 6 x 1019/cm3 was found to increase the (001) growth rate at low temperatures, but decrease the rate at higher temperatures, during gas-source molecular beam epitaxy using Si2H6 and B2H6. A study was made of (001) samples with B coverages that ranged from less than 0.05, to about 0.5, of a monolayer. They were prepared by exposing clean (001) 2 x 1 wafers to B2H6 doses of between 2 x 1017 and 4 x 1020/cm2 at 200 to 400C. The samples were then heated to 700C in order to desorb H, cooled to 200C, and were exposed to atomic D to give saturation coverage. The D2 temperature-dependent desorption spectra exhibited 2 and 1 peaks, that were due to di-deuteride and mono-deuteride desorption at 405 and 515C, as well as new B-induced 2* and 1* peaks at 330 and 470C. It was found that increasing the B coverage increased the area under 2* and 1* peaks at the expense of 2 and 1 peaks. Also, the total D coverage decreased continuously from about 1.23 monolayers in the absence of B, to about 0.74 of a monolayer at a B coverage of 0.5 of a monolayer. It was proposed that the observed B-induced decrease in the Si*-D bond strength was due to charge transfer and increased Si* dimer strain. Here, Si* represented surface Si atoms which were bonded to second-layer B atoms. The Si* to B charge transfer also deactivated Si surface dangling bonds and caused a decrease in the D coverage.

H.Kim, G.Glass, S.Y.Park, T.Spila, N.Taylor, J.R.Abelson, J.E.Greene: Applied Physics Letters, 1996, 69[25], 3869-71