Elsevier

Journal of Crystal Growth

Volume 511, 1 April 2019, Pages 127-131
Journal of Crystal Growth

Fe delta-doped (In,Fe)Sb ferromagnetic semiconductor thin films for magnetic-field sensors with ultrahigh Hall sensitivity

https://doi.org/10.1016/j.jcrysgro.2019.01.030Get rights and content

Highlights

  • Epitaxial growth of Fe delta-doped (In,Fe)Sb thin films.

  • Intrinsic ferromagnetism confirmed by MCD spectroscopy measurements.

  • TC lower than the uniformly-doped (ln,Fe)Sb with the same average Fe concentration.

  • Much higher Hall sensitivity of the δ-doped samples than those of uniformly-doped.

  • Very promising for highly sensitive anomalous Hall effect sensors.

Abstract

We have grown Fe δ-doped (In,Fe)Sb thin films by low-temperature molecular beam epitaxy for magnetic-field sensors with ultrahigh Hall sensitivity. Magnetic circular dichroism spectroscopy measurements indicate intrinsic ferromagnetism in the Fe δ-doped (In,Fe)Sb layers. Although the Fe δ-doped (In,Fe)Sb thin films have lower Curie temperature than the Fe uniformly-doped (ln,Fe)Sb with the same average Fe concentration, their anomalous Hall effect is much stronger. The Hall sensitivity of the Fe δ-doped (In1−〈x,Fex)Sb sample with an average Fe concentration 〈x〉 = 17% reaches 1522 Ω/T at room temperature, which is much higher than those of Fe uniformly-doped (In,Fe)Sb, (Ga,Fe)Sb, and commercial InSb Hall sensors.

Introduction

Ferromagnetic semiconductors (FMSs) belong to a family of materials with both properties of semiconductors and ferromagnets. In particular, transition metal (TM)-doped III-V FMSs have been intensively studied because of their compatibility with III-V electronic and photonic semiconductor devices. Recently, Fe-doped narrow-gap FMSs have generated great interest since it is possible to fabricate both p-type FMSs and n-type FMSs with Curie temperature (TC) higher than room temperature [1], [2], [3], [4]. Among them, n-type FMS (In,Fe)Sb is promising for device applications because its TC reaches room temperature at relatively low Fe concentration (16%) and it shows large anomalous Hall effect (AHE), which may be applied to magnetic-field sensors with ultrahigh Hall sensitivity [4]. It is well-known that in a FMS, the Hall resistivity, ρxy, is given by ρxy = RHH + RAHEM, where RH is the ordinary Hall coefficient, RAHE is the anomalous Hall coefficient, H is the external magnetic field, and M is the magnetization. Since RAHE >> RH, a FMS with relatively high TC and strong AHE may be used for magnetic-field sensors with ultrahigh sensitivity. While there are several studies of magnetic-field sensors using AHE [5], [6], [7], [8], [9], [10], the high sensitivities were observed only at low temperature or low magnetic field. In contrast, we show that (In,Fe)Sb can be used for the magnetic-field sensors with high Hall sensitivity at room temperature in the wider range of magnetic field.

In this study, to realize (In,Fe)Sb with ultrahigh Hall sensitivity, we have grown Fe δ-doped (In1−〈x,Fex)Sb thin films with various average Fe concentrations (〈x〉 = 5–20%) and investigated their magnetic properties as well as AHE. The magnetic properties were characterized by magnetic circular dichroism (MCD) spectroscopy, which indicates intrinsic ferromagnetism in the Fe δ-doped (In,Fe)Sb thin films. From the MCD intensity vs. magnetic field characteristics, we estimated TC of Fe δ-doped (In,Fe)Sb thin films by Arrott plots. The TC of the Fe δ-doped (In1−〈x,Fex)Sb tends to be lower than that of the Fe uniformly-doped (In1−x,Fex)Sb. However, the Fe δ-doped (In,Fe)Sb thin films show much larger AHE than the Fe uniformly-doped (In,Fe)Sb thin films, which is very promising for ultrahigh sensitive Hall sensors at room temperature.

Section snippets

Experiments and results

The schematic structure of our samples is shown in Fig. 1(a). The Fe δ-doped (In,Fe)Sb thin films were grown on semi-insulating GaAs (0 0 1) substrates by using low-temperature molecular beam epitaxy (LT-MBE) and the Fe δ-doping technique. First, we grew a 50-nm-thick GaAs buffer layer to obtain a smooth GaAs surface at 560 °C. Then, 10-nm-thick AlAs and 100-nm-thick AlSb buffer layers were grown at 560 °C and 480 °C, respectively, to relax the lattice mismatch between the GaAs layer and the

Summary

In summary, we have grown Fe δ-doped (In1−〈x,Fex)Sb thin films with various average Fe concentrations (〈x〉 = 5–20%) by using LT-MBE and the Fe δ-doping technique. The magneto-optical properties characterized by MCD spectroscopy indicate the intrinsic ferromagnetism in the Fe δ-doped (In,Fe)Sb thin films. The TC of the Fe δ-doped (In1−〈x,Fex)Sb tends to be lower than that of the Fe uniformly-doped (In1−x,Fex)Sb with the same x   = 〈x〉. On the other hand, the Fe δ-doped (In,Fe)Sb thin films

Acknowledgment

This work is supported by Grants-in-aid for Scientific Research, CREST Program (No. JPMJCR1777) of Japan Science and Technology Agency, the Nanotechnology Platform 12025014 from MEXT, and Spintronics Research Network of Japan (Spin-RNJ).

References (17)

  • S.S. Das et al.

    Mater. Lett.

    (2015)
  • K. Ando et al.

    J. Magn. Magn. Mater.

    (2004)
  • J. Smit

    Physica

    (1955)
  • J. Smit

    Physica

    (1958)
  • P.N. Hai et al.

    Appl. Phys. Lett.

    (2012)
  • N.T. Tu et al.

    Appl. Phys. Lett.

    (2014)
  • N.T. Tu et al.

    Appl. Phys. Lett.

    (2016)
  • N.T. Tu et al.

    Appl. Phys. Exp.

    (2018)
There are more references available in the full text version of this article.

Cited by (7)

  • Structural and optical properties of Fe doped InSb bulk systems

    2022, Materials Today: Proceedings
    Citation Excerpt :

    Recently Y Ni et al. [6] have prepared n-type and p-type Ferromagnetic semiconductors and reported the presence of ultra-sensitive hall effect at relatively higher curie temperature than room temperatures. Fe doped InSb materials are even preferred for device fabrications (Hall measurement and hysteresis measurement devices) because of their ultrahigh Hall sensitivity [7]. This peculiar property makes the InSb system more favourable for photonics, spintronics and optoelectronic devices applications.

  • Electric bias-controlled switching of magnetization of ferrimagnetically coupled Mn delta-layers in a GaAs-AlGaAs quantum well

    2020, Journal of Magnetism and Magnetic Materials
    Citation Excerpt :

    Therefore, it would be important to investigate if the III-V semiconductor-based structures with Fe delta-layers can be fabricated for the ultrafast switching. Presently, however, there are no reports on successful increase of the Curie temperature by Fe delta-doping of a III-V semiconductor [44]. N.V. Agrinskaya: Methodology, Writing - review & editing.

View all citing articles on Scopus
View full text