We study the contact resistance of strongly doped ferromagnetic/non-magnetic semiconductors structure (p+ - F/n+ -N), working as spin injectors and spin extractors. Because of the strong effect that the barrier shape has on the tunneling probabilities, we evaluate, as accurately as possible, the quantum-mechanical spin-dependent transmission across the Esaki barrier built up at the p-n interface. To simplify the discussion and calculation of transmission coefficients through the Esaki barrier, we concentrate here on the structure p+ - F/n+ -N, without a stop layer I. We evaluate the spin injection and spin extraction transmission coefficients T↑↑ and T↓↓, and the spin transmission polarization as functions of bias potential, exchange interaction energy and Fermi energy level for specific realizations of the structure p+-Ga1-xMnxAs/n+-GaAs.
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