PAA-based etchant, and methods in which this etchant is used

A wet etching with: about 1.0 wt .-% to about 50 wt .-% peracetic acid (PAA); and a fluorinated acid; wherein the ratio of PAA is sufficient in the wet etching composition to ensure a ratio of the etching rate of p-doped SiGe to that of p-doped Si, which is essentially equal to the ratio of the etching rate of n-doped SiGe to that of n-doped Si is.