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Voltage-controlled spin injection in a (Ga,Mn)As∕(Al,Ga)As Zener diode

P. Van Dorpe, W. Van Roy, J. De Boeck, G. Borghs, P. Sankowski, P. Kacman, J. A. Majewski, and T. Dietl
Phys. Rev. B 72, 205322 – Published 15 November 2005
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  • INTRODUCTION
  • THE THEORETICAL APPROACH
  • RESULTS
  • DISCUSSION
  • SUMMARY
  • ACKNOWLEDGEMENTS
    • References

    Abstract

    The spin polarization of the electron current in a p−(Ga,Mn)As∕n−(Al,Ga)As Zener tunnel diode, which is embedded in a light-emitting diode, is studied theoretically. A series of self-consistent simulations determines the charge distribution, the band bending, and the current-voltage characteristics for the entire structure. In order to study the current spin effects the spin dependent tight-binding Hamiltonian is implemented into the Landauer-Büttiker scheme. This dual approach allows us to describe the experimentally observed high magnitude and strong bias dependence of the current spin polarization.

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    • Received 3 March 2005

    DOI:https://doi.org/10.1103/PhysRevB.72.205322

    ©2005 American Physical Society

    Authors & Affiliations

    P. Van Dorpe*, W. Van Roy, J. De Boeck, and G. Borghs

    • IMEC, Kapeldreef 75, B-3001 Leuven, Belgium

    P. Sankowski and P. Kacman

    • Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warszawa, Poland

    J. A. Majewski

    • Institute of Theoretical Physics, Warsaw University, ul. Hoża 69, 00-681 Warszawa, Poland

    T. Dietl

    • Institute of Physics, Polish Academy of Sciences and ERATO Semiconductor Spintronics Project, al. Lotników 32/46, 02-668 Warszawa, Poland and Institute of Theoretical Physics, Warsaw University, ul. Hoża 69, 00-681 Warszawa, Poland

    • *Electronic address: pvandorp@imec.be

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    Vol. 72, Iss. 20 — 15 November 2005

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    Images

    • Figure 1
      Figure 1
      The degree of injected spin polarization measured at 4.6K as a function of the applied bias voltage (a) and the current (b) from Ref. 4.Reuse & Permissions
    • Figure 2
      Figure 2
      The measured at 4.6K (Ref. 4) current (solid line) and the simulated current for 40K (dashed line) as a function of the applied bias voltage. The voltage axis of the simulated curve has been shifted by 0.25V to take into account the offset in the threshold voltage where tunneling starts. The insets show the simulated conduction and valence band profiles at (a) 1.81V and (b) 3.0V bias. The grey-colored area represents the (Ga,Mn)As injector.Reuse & Permissions
    • Figure 3
      Figure 3
      The Al concentration as a function of the depth near the (Ga,Mn)As∕GaAs tunnel diode (a). The band diagram (solid lines) and the carrier generation (dark filled) due to interband tunneling at 1.81V (b) and 3V bias voltage (c). The light filled areas represent the (Ga,Mn)As injector. The dotted arrows indicate the tunneling of valence electrons from (Ga,Mn)As into the conduction band of GaAs.Reuse & Permissions
    • Figure 4
      Figure 4
      The hole concentration (left) and the carrier generation due to interband tunneling (right) at different values of the applied bias voltage near the (Ga,Mn)As∕GaAs interface. The grey-colored area represents the (Ga,Mn)As injector.Reuse & Permissions
    • Figure 5
      Figure 5
      The carrier generation due to impact ionization and to interband tunneling at different values of the applied bias voltage. The grey-shaded areas represent the carrier generation due to interband tunneling in the (Ga,Mn)As valence band and the GaAs conduction band.Reuse & Permissions
    • Figure 6
      Figure 6
      Scheme of the structure description used in the calculations: (a) the band profile of the entire LED calculated using Medici for V0=1.81V; (b.1) in the tight-binding calculations only the Zener diode region is considered; (b.2) a linear band bending given by an applied bias ΔV is added; (b.3) the band profile used in the tight-binding calculations is a sum of (b.1) and (b.2).Reuse & Permissions
    • Figure 7
      Figure 7
      The calculated bias dependence of the current polarization for the structure in Fig. 6b.Reuse & Permissions
    • Figure 8
      Figure 8
      Scheme of the (abrupt) (Ga,Mn)As∕GaAs p−n-diode structure used in the simplified tight-binding calculations at zero and reverse bias.Reuse & Permissions
    • Figure 9
      Figure 9
      (a) The calculated valence band intersection at the Fermi energy of (Ga,Mn)As for a hole concentration of 3.5×1020cm−3 and the tunneling current as function of kx and ky. (b) The magnitude of the tunneling currents at an applied voltage of 1mV for both the majority spins and the minority spins for different k‖ vectors in the structure presented in Fig. 8.Reuse & Permissions
    • Figure 10
      Figure 10
      The complex band structure of GaAs, adopted from Ref. 6. The light-hole band (LH) connects to the lower conduction band (CB), while the heavy-hole band (HH) connects to a higher energy conduction band.Reuse & Permissions
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