ELECTRONIC-STRUCTURE OF FM SEMICONDUCTOR/FM SPIN TUNNELING STRUCTURES/

We have calculated the electronic structure of the spin-dependent tunn eling structures, Fe\Ge\Fe and Fe\GaAs\Fe, using first principles tech niques. We find that there is a large charge transfer from the metal l ayer to the semiconductor layer; 0.21 electrons are transferred from F e to Ge and 0.27 electrons are transferred from Fe to GaAs at each int erface. The density of states of the interfacial metal layer is dramat ically different from the other metal layers; there is a large peak in the density of states at the Fermi energy for the minority electrons. The electronic structure of the semiconductor layer is quite differen t for the majority and the minority spins although its total magnetic moment is negligible. Our results suggest that the theory of spin-depe ndent tunneling using the simple model of a potential barrier or a mod el based on densities of states taken from bulk band structures may no t apply to these systems. (C) 1997 American Institute of Physics.