  Here we show the room temperature integrated detection of the helicity of
photons with 1300 nm wavelength, via spin- photodiodes based on fully epitaxial
Fe/MgO/Ge(001) heterostructures. These devices convert the photon helicity in a
variation of the photocurrent ({\Delta}I) for opposite orientations of the Fe
magnetization. We found {\Delta}I on the order of 5.9% for 100% circularly
polarized light, both in the forward and the reverse bias, with a contribution
of 0.8% from the Fe dichroic light absorption and of 5.1% from the spin
filtering of photo-generated carriers crossing the Fe/MgO/Ge tunneling barrier.
