We have investigated the photoluminescence (PL) and electroluminescence (EL) at 1.54 mu m from excited Er3+ ions in erbium- and oxygen-doped Si and SiGe samples which were grown completely by molecular beam epitaxy (MBE). The good crystal quality after growth allowed PL and EL characterization of as grown samples without further annealing. For the PL measurements two series of samples with alternating Si/Si1-xGex layers have been fabricated, one in which erbium and oxygen were placed into the Si1-xGex layers and the other one with the dopants in the Si layers. At low temperatures an enhancement of the PL signal is observed when the dopants are placed into the Si1-xGex layers rather than into the Si layers. With increasing temperature these samples show a more pronounced decrease of PL intensity than those with the doped Si layers. Samples which have been processed as pn diodes show electroluminescence up to 300 K.