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[19p-N302-2] N-type and p-type ferromagnetic semiconductors: High Curie temperature and heterostructure devices
Keywords:Ferromagnetic semiconductor, magnetic proximity effect, magnetoresistance
Ferromagnetic semiconductors (FMSs) with high Curie temperature (TC) are strongly required for spintronics device applications. In this study, we present a new class of FMSs with high TC, Fe-based narrow-gap III-V FMSs. Using low-temperature molecular beam epitaxy, we have successfully grown both p-type FMS [(Ga,Fe)Sb, (Al,Fe)Sb] and n-type FMSs [(In,Fe)As, (In,Fe)Sb]. Intrinsic room-temperature ferromagnetism has been observed in (Ga1-x,Fex)Sb with x > 23% and (In1-x,Fex)Sb with x > 16%, which are promising for practical spintronic devices operating at ambient temperature.
In an Esaki diode composed of a 50 nm-thick n-type FMS (In,Fe)As (6% Fe) / p+ InAs:Be, we found that the magnetic-field-dependence of the current flowing through the pn junction can be largely controlled, both in sign and magnitude, with the bias voltages V. Furthermore, we found that the current flowing in a nonmagnetic n-type InAs quantum well (QW) that is interfaced to an insulating p-type (Ga,Fe)Sb layer exhibits a giant change of approximately 80% at high magnetic field and that its magnitude can be controlled by ten-fold using a gate. The mechanism for this large magnetoresistance is attributed to a strong magnetic proximity effect (MPE) at the InAs/(Ga,Fe)Sb interface. It was found that a spin splitting in the InAs QW is induced by MPE, which can be varied between 0.17 meV and 3.8 meV by the gate voltage. These new magnetotransport phenomena of the Fe-doped FMS-based devices provide novel functionalities for the future spin-based electronics.
In an Esaki diode composed of a 50 nm-thick n-type FMS (In,Fe)As (6% Fe) / p+ InAs:Be, we found that the magnetic-field-dependence of the current flowing through the pn junction can be largely controlled, both in sign and magnitude, with the bias voltages V. Furthermore, we found that the current flowing in a nonmagnetic n-type InAs quantum well (QW) that is interfaced to an insulating p-type (Ga,Fe)Sb layer exhibits a giant change of approximately 80% at high magnetic field and that its magnitude can be controlled by ten-fold using a gate. The mechanism for this large magnetoresistance is attributed to a strong magnetic proximity effect (MPE) at the InAs/(Ga,Fe)Sb interface. It was found that a spin splitting in the InAs QW is induced by MPE, which can be varied between 0.17 meV and 3.8 meV by the gate voltage. These new magnetotransport phenomena of the Fe-doped FMS-based devices provide novel functionalities for the future spin-based electronics.