Enhancement of thermal diffusion of delta-doped Sb in SiGe

Distribution of delta-doped Sb atoms in a Si1-xGex layer was studied by usi ng a new method combining chemical treatment and inductively-coupled-plasma mass spectrometry, and thermal diffusion of the Sb atoms was studied by se condary-ion mass spectrometry (SIMS). The delta doping was performed as fol lows: First, 0.1-monolayer Sb atoms were deposited on Si1-xGex surfaces and embedded by evaporating amorphous Si1-xGex layers on them at room temperat ure in order to reduce the surface segregation phenomenon. Then the amorpho us Si1-xGex layers were crystallized by heating at 600 degrees C. The initi al width of the Sb-doping profile is only about 1 nm in pure Si. The width increases with increasing Ge content in the Si1-xGex layers. Moreover, seco ndary ion mass spectrometry (SIMS) analysis shows that Ge atoms strongly en hance the thermal diffusion of Sb, and the diffusion enhancement is attribu ted to the decrease in activation energy of diffusion caused by the existen ce of Ge atoms in the Si1-xGex layers. (C) 2000 Elsevier Science S.A. All r ights reserved.