Boron doping concentrations ≳6×1019cm−3were found to increase Si(001) growth ratesRSiat low temperatures while decreasingRSiat higher temperatures during gas‐source molecular beam epitaxy (GS‐MBE) from Si2H6and B2H6. In order to probe the mechanisms governing these effects, Si(001) samples withBcoverages &thgr;Branging from <0.05 to &bartil;0.5 ML were prepared by exposing clean Si(001)2×1 wafers to B2H6doses between 2×1017and 4×1020cm−2at 200–400 °C. The samples were then heated to 700 °C to desorb the hydrogen, cooled to 200 °C, and exposed to atomic deuterium until saturation coverage.D2temperature programmed desorption spectra exhibit &bgr;2and &bgr;1peaks due to dideuteride and monodeuteride desorption at 405 and 515 °C as well as newB‐induced peaks, &bgr;2*and &bgr;1*, at 330 and 470 °C. Increasing &thgr;Bincreases the area under &bgr;2*and &bgr;1*at the expense of &bgr;2and &bgr;1. Moreover, the totalDcoverage continuously decreases from &bartil;1.23 ML in the absence ofBto &bartil;0.74 ML at &thgr;B=0.5 ML. We propose that the observedB‐induced decrease in the Si*‐Dbond strength, where Si* represents surface Si atoms bonded to second‐layerBatoms, is due to charge transfer and increased Si* dimer strain. The Si* toBcharge transfer also deactivates Si surface dangling bonds causing the decrease in &thgr;D. These results are used to explain the GS‐MBE growth kinetics. ©1996 American Institute of Physics.