> I m looking for a wet etching solution in order to etch Germanium?
> Can someone give me an advice or references?

Heated H2O2 will etch Ge.
See John Heck's Ph.D. dissertation at BSAC at
http://www-bsac.eecs.berkeley.edu/archive/john_heck_phd.pdf
Chapter 3 covers etching.
For polycrystalline Ge, which should etch faster than single-crystal Ge,
he measured the following lateral etch rates (vertical should be about the
same):
T (C)                   ER (um/min)
-----                   -----------
74                      0.15
83                      0.22
93                      0.31
102                     0.40

        --Kirt Williams Agilent Technologies