The damage produced by implanting, at room temperature, 3-&mgr;m-thick relaxed Si1−xGexalloys of high crystalline quality with 2 MeV Si+ions has been studied as a function of Ge content (x=0.04, 0.13, 0.24, or 0.36) and Si dose in the dose range 1010–2×1015cm−2. The accumulation of damage with increasing dose has been investigated by Rutherford backscattering spectrometry, optical reflectivity depth profiling, and transmission electron microscopy. An enhanced level of damage, and a strong decrease in the critical dose for the formation of a buried amorphous layer in Si1−xGexis observed with increasingx. Electron paramagnetic resonance studies show that the dominant defects produced by the implantation are Si and Ge dangling bonds in amorphouslike zones of structure similar toa-Si1−xGexfilms of the samex, and that the effect of increasing the ion dose is primarily to increase the volume fraction of material present in this form until a continuous amorphous layer is formed. A comparative study of the optically determined damage in the alloys with the use of a damage model indicates a significant increase in the primary production of amorphous nuclei in the alloys of Ge contentx>0.04. ©1997 American Institute of Physics.