A comparison of strain relief in SiGe alloy layers during high temperature
annealing and solid phase epitaxial crystallisation (SPEC) has shown that
layers which are thermodynamically stable are also fully strained following
SPEC, whereas metastable layers that relax at high temperatures also relax
during SPEC. This is illustrated by the fact that a uniform SiGe layer with
x=0.085 is stable during annealing at 1100°C for 60 sec and is fully
strained following SPEC. In contrast, a uniform layer with x=0.17, which was
fully strained as-grown by molecular beam epitaxy (MBE), is shown to relax
during high temperature annealing and during SPEC.
A depth dependent SPEC velocity is observed for metastable layers, with a
decrease in velocity as the alloy layer begins to crystallise and an
increase in velocity as strain relaxation proceeds.