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Ferromagnetic semiconductors (FMSs) with high Curie temperature (TC) are highly desired for spintronics device applications. So far, the mainstream study of FMSs is the Mn-doped III-V FMSs;, however they are only p-type and TC is much lower than 300K. To search for new FMSs with high-performance, there have been world-wide efforts that were mainly concentrated on wide-gap materials. However, reliable and systematic results have not yet been presented.
In this study, we present an alternative approach by using Fe instead of Mn as the magnetic dopants in narrow-gap III-V semiconductors; InAs, GaSb, and InSb. In these Fe-based FMSs, because the Fe atoms are in the isoelectronic Fe3+ state, the carrier type (electrons or holes) can be controlled independently by co-doping non-magnetic dopants. These carriers reside in the conduction band (CB) or the valence band (VB) of the host semiconductors and thus move faster with higher coherency. Using low-temperature molecular beam epitaxy, we have successfully grown single-phase thin-film crystals of both p-type FMS [(Ga,Fe)Sb [2]] and n-type FMSs [(In,Fe)As [3], (In,Fe)Sb [4]]. TC increases monotonically with the Fe content; and there is a tendency that TC is higher as the bandgap is narrower. Intrinsic room-temperature ferromagnetism has been observed in (Ga1-x,Fex)Sb with x > 23% [2] and (In1-x,Fex)Sb with x > 16% [4]. In n-type FMS (In,Fe)As, large spontaneous spin splitting in the CB was observed, which is the first in all FMSs [5]. These results indicate that the Fe-doped III-V FMSs are promising for spintronic devices operating at room temperature.
[1] N. T. Tu et al., APL 108, 192401 (2016). [2] P. N. Hai, APL 101, 182403 (2012). [3] N. T. Tu et al., arXiv:1706.00735 (2017). [4] L. D. Anh et al., PRB 92, 161201(R) (2015). [5] L. D. Anh et al., Nat. Commun. 7, 13810 (2016).
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