Effect of thermal processing on mobility in strained Si/strained Si1-yGey on relaxed Si1-xGex (x<y) virtual substrates

Annealing effects on hole and electron mobility in dual-channel structures consisting of strained Si and Si1-yGey on relaxed Si1-xGex layers (x=0.3/y=0.6, and x=0.5/y=0.8) were studied. Hole mobility decreases sharply, but electron mobility is quite immune to annealing conditions of 800 degreesC, 30 min or 900 degreesC, 15 s. The hole mobility decrease is more severe in dual-channel structures with higher Ge contents. Hole mobility degradation is a direct result of Ge outdiffusion from the Si1-yGey layer, and the resulting decreased Ge content. Ge diffusion preferentially towards the Si1-xGex buffer layer, rather than the Si cap layer, is a reason that electron mobility is highly immune to such annealing. (C) 2004 American Institute of Physics.