Strain relaxation and threading dislocation density in helium-implanted and annealed Si1-xGex/Si(100) heterostructures

Strain relaxation and threading dislocation densities in Si1-xGex (0.15<x<0.30) produced by He implantation and annealing have been investigated using x-ray diffraction and transmission electron microscopy. The degree of strain relaxation is very sensitive to the SiGe layer thickness; only small differences in strain relaxation are obtained when the helium dose and energy are varied over a relatively wide range. In contrast, the threading dislocation density is strongly influenced by the implantation dose and depth. A composite parameter, the He dose in the SiGe layer (He(SiGe)), calculated from He profiles simulated using the program Stopping and Range of Ions in Matter (SRIM2000), correlates well with the threading dislocation density. We have found that to achieve a low threading dislocation density, <5x10(7) cm(-2), He(SiGe) must be less than 1x10(15) cm(-2). (C) 2004 American Institute of Physics.