INFLUENCE OF GERMANIUM CONTENT ON THE PHOTOLUMINESCENCE OF ERBIUM-DOPED AND OXYGEN-DOPED SIGE GROWN BY MOLECULAR-BEAM EPITAXY

The photoluminescence at 1.54 mu m of erbium-and oxygen-doped Si/Si1-x Gex samples grown completely by molecular beam epitaxy has been invest igated for germanium concentrations ranging from x = 0 to x = 0.165. T he dopants were either placed into the Si1-xGex or into the Si layers of an alternating Si/Si1-xGex layer structure. Because of the good cry stal quality after growth, it was possible to obtain all luminescence data from as-grown samples without annealing. We observed a decrease i n photoluminescence (PL) intensity and a stronger temperature dependen ce with increasing Ge content. For samples with the same Si/Si1-xGex l ayer structure, an enhancement of PL intensity at low temperature was seen when erbium and oxygen were placed into the Si1-xGex layers rathe r than into the Si layers. We attribute this effect to a capture of ph otogenerated carriers in the Si1-xGex layers. (C) 1997 American Instit ute of Physics.