Enhancement of thermal diffusion of delta-doped Sb in SiGe

Abstract

Distribution of delta-doped Sb atoms in a Si1−xGex layer was studied by using a new method combining chemical treatment and inductively-coupled-plasma mass spectrometry, and thermal diffusion of the Sb atoms was studied by secondary-ion mass spectrometry (SIMS). The delta doping was performed as follows: First, 0.1-monolayer Sb atoms were deposited on Si1−xGex surfaces and embedded by evaporating amorphous Si1−xGex layers on them at room temperature in order to reduce the surface segregation phenomenon. Then the amorphous Si1−xGex layers were crystallized by heating at 600°C. The initial 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, secondary ion mass spectrometry (SIMS) analysis shows that Ge atoms strongly enhance the thermal diffusion of Sb, and the diffusion enhancement is attributed to the decrease in activation energy of diffusion caused by the existence of Ge atoms in the Si1−xGex layers.