Electrical detection of optically pumped spin polarization in Ge
  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. 
C. Rinaldi, M. Cantoni, D. Petti, M. Leone, N. M. Caffrey, S. Sanvito,   and R. Bertacco
cond-mat.mtrl-sci