Strain relaxation in strained-Si layers on SiGe-on-insulator substrates

摘要

Misfit strain relaxation in tensile-strained Si grown at 600℃ on (0 0 1) SiGe-on-insulator substrates is experimentally studied for a tensile strain range between 0.4 and 1.2%. The critical thickness is found to be rather thinner than Houghton's critical thickness for a compressively-mismatched SiGe/Si(0 0 1) system. The thinner critical thickness in tensile-strained Si is attributed to the fact that the stress-relieving misfit dislocations are 90° partial dislocations, instead of 60° misfit dislocations for the compressive SiGe/Si(0 0 1) system. With increasing strained-Si layer thickness thicker than the critical thickness, 60° misfit dislocation is found to be increasingly formed but the strain relaxation is sluggish. For a supercritical thickness ten times thicker than the critical thickness the tensile strain mostly remains. The initial strain relaxation is discussed in terms of the misfit dislocation morphology.