We have studied in situ boron, arsenic, and phosphorus doping of epitaxial silicon and Si1-xGex layers grown on silicon substrates at 620 degrees C and at very low pressure (similar to 7 mTorr) with silane, germane, and diborane, and arsine and phosphine diluted in silane as gas sources. Structural quality was chacterized by cross-sectional transmission electron microscopy and the germanium and dopant depth profiles were probed by secondary ion mass spectrometry. The results confirmed that strained Si/Si1-xGex/Si heterostructures with 13 atom percent germanium doped to 2 x 10(20) baron atom/cm(3) and 5 x 10(19) arsenic atom/cm have been achieved. Phosphorus doped Si1-xGex/Si multilayer structures with highly perfect surface Si1-xGex and silicon layers were also obtained. The addition of arsine and phosphine were found to severely degrade the growth rates of both silicon and Si1-xGex layers. Germanium incorporation appeared to enhance the n-type doping process by compensating the depressed growth rate resulted from surface poisoning and by improving the abruptness of dopant profiles. However, deposition of Si1-xGex was not greatly affected by boron doping.