Phosphorus doping of silicon during growth by molecular beam epitaxy (MBE) has been investigated in the temperature regime 700 degrees C to 870 degrees C. By designing a growth sequence that fully accounts for the P deposited in a delta-doped layer, and then tracks the P as it segregates into the undoped Si and traps the surface P in a low temperature Si cap, it was determined that the onset of significant P evaporation during growth occurred at a substrate temperature of 663 degrees C +/- 10 degrees C. The P sublimation process had an activation energy of 199 kJ/mol +/- 22 kJ/mol. Published by Elsevier B.V.