The role of low temperature growth defects for the stability of strained Si/Si1−xGex heterostructures

High-resolution reciprocal lattice mapping (HRRLM) has been used to characterize the strain and thermal stability of undoped, Sb-, and B-doped Si/Si1−xGex (0.16≤x≤0.20) heterostructures grown at temperatures from 300 to 620°C. HRRLM shows no mosaic broadening for Si1−xGex as-grown samples with layer thickness up to 1500 Å. Annealing of undoped Si1−xGex layers grown at 300°C or B- or Sb-doped layers grown at 400°C leads to the onset of relaxation already at 500°C. This is in contrast to undoped Si1−xGex layers grown at 600°C which appear to be stable at this annealing temperature. The significantly reduced relaxation temperature in doped layers or layers grown at low temperature is attributed to a decreased activation barrier for nucleation of misfit dislocations in layers with a high concentration of point defects including dopant atoms.