Photo-assisted tunneling at ferromagnet/semiconductor interfaces

We have measured the polarization-dependent photoresponse of ferromagnet-insulator-(III–V) semiconductor thin film tunnel structures as a function of wavelength. When the structures have no interfacial barrier, we find that the response agrees well with calculations of magneto-optical transmission through the magnetic overlayer. However, when a tunnel barrier is present and excitation nearly resonant with the semiconductor bandgap, we observe significant deviations from the magneto-optical effects. These deviations are attributed to spin-dependent electron transmission from the III–V semiconductor acting as a spin-polarized source of tunneling electrons.