1:30 PM - 1:45 PM
▲ [14p-C41-2] Bias-dependent magneto-conductance in n-type ferromagnetic semiconductor (In,Fe)As-based Esaki diodes
Keywords: spin Esaki diode, magnetoresistance, n type ferromagnetic semiconductor
Here we study spin-dependent transport in an Esaki diode composed of a 50 nm-thick n-type (In,Fe)As (6% Fe)/5 nm-thick InAs/250 nm-thick p+ InAs:Be (Be concentration 5×1018 cm-3)/p+ type InAs (001) substrate. At bias voltage V smaller than 460 mV, the diode shows small positive magneto-conductance (MC) (~0.5%), which is typical of FMSs. However, when V > 460 mV, the MC changes its sign and its magnitude increases with V, reaching -7.4% (at 1T) at V = 650 mV. In the band profiles of the pn junction of this diode, the conduction band (CB) of (In,Fe)As is spin-split and there is an Fe-related impurity band (IB) right below the CB bottom . At small V, electrons tunnel from the CB of (In,Fe)As to the valence band (VB) top of p-InAs, while the tunneling of electrons from IB (d orbitals) is prohibited by the orbital symmetry. However, at V > 460 mV where the energy of CB and IB of (In,Fe)As is aligned with the energy of empty CB of p-InAs, the current is diffusive and the prohibition by the orbital symmetry is relaxed. Therefore, electrons in the IB start to flow into the p-InAs CB and experience strong s-d scattering at the interface. We show that it is possible to explain the change in sign and magnitude of the MC by the onset of s-d scattering, which is caused by the contribution of the IB electrons in (In,Fe)As to the diffusive current at large positive bias voltages.
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