The 77th JSAP Autumn Meeting, 2016

Presentation information

Oral presentation

10 Spintronics and Magnetics » 10.4 Semiconductors, organic, optical, and quantum spintronics

[14p-C41-1~21] 10.4 Semiconductors, organic, optical, and quantum spintronics

Wed. Sep 14, 2016 1:15 PM - 7:00 PM C41 (Nikko Toki A)

Shinobu Ohya(Univ. of Tokyo), Hiromasa Shimizu(TUAT)

1:30 PM - 1:45 PM

[14p-C41-2] Bias-dependent magneto-conductance in n-type ferromagnetic semiconductor (In,Fe)As-based Esaki diodes

Anh Duc Le1, Nam Hai Pham2,3, Masaaki Tanaka1,3 (1.EEIS, Tokyo Univ., 2.Tokyo Ins. Tech., 3.CSRN, Tokyo Univ.)

Keywords: spin Esaki diode, magnetoresistance, n type ferromagnetic semiconductor

Ferromagnetic semiconductors (FMSs) have been attracting a lot of attentions because they provide opportunities to integrate spin-dependent phenomena into semiconductor electronic devices. Among various FMSs, (In,Fe)As is a promising one, because it is the only n-type electron-induced III-V-based FMSs that has been realized so far [1]. Quantum size effects were also observed in (In,Fe)As thin films [2], and electrical control of the ferromagnetism of (In,Fe)As quantum wells by wavefunction engineering has been demonstrated [3].
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 [4]. 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.
Reference: [1] P. N. Hai, et al., APL 101, 182403 (2012). [2] L. D. Anh, et al., APL 104, 042404 (2014). [3] L. D. Anh, et al., PRB 92, 161201(R) (2015). [4] L. D. Anh et al., 2016 JSAP Spring Meeting 19p-W241-2.