Very high spin polarization in GaAs by injection from a (Ga,Mn)As Zener diode

Abstract

We demonstrate an electrically injected electron spin polarization in GaAs of 80% at 4.6 K by interband tunneling from the valence band of (Ga,Mn)As into an (Al,Ga)As light-emitting diode. The polarization is analyzed by the oblique Hanle effect and vanishes at 120 K, the Curie temperature of the (Ga,Mn)As injector. The temperature and the bias dependence of the polarization are explained in terms of the properties of the (Ga,Mn)As/GaAs diode.

Tight-binding model of spin-polarized tunnelling in (Ga,Mn)As-based structures

“…The spin injection in the Zener diode, again like in TMR, depends crucially on the con- tent of magnetic ions in the Ga 1−x Mn x layer. For x = 0.08 we obtain the spin current polarization to be of the order of 60%, what agrees very well with the experimental observations [7].…”

“…As a second application of the developed formalism for spin-dependent tunneling, we consider the Zener diode in which high polarization of the spin current has been recently observed [7]. Alas, in approaches involving transfer matrix formalism, computational constraints hinder the simulations of the spin-dependent tunneling through the whole device used in the experiments in Ref.…”

“…Furthermore, peculiar behavior of TMR was observed in nanoconstrictions [5] as well as when the holes in (Ga,Mn)As were at the localization boundary [6]. Also, it has been demonstrated that highly spin polarized electron current, with polarization reaching 80%, can be obtained from a p-(Ga,Mn)As/n-GaAs Zener diode [7].…”

Voltage-controlled spin injection in a(Ga,Mn)As∕(Al,Ga)Dorpe1, Roy2, Boeck3 et al. 2005Phys. Rev. BSelf Cite

“…2,3 Recently, an injected spin polarization up to 80% at 4.6 K has been demonstrated in a (Ga,Mn)As based spin-light emitting diode (LED) using Zener tunneling. 4 Moreover, the degree of injected spin polarization exhibits a strong dependence on the applied bias. The spin polarization reaches its maximum just above the electroluminescence threshold and decreases dramatically at higher bias.…”

“…The device considered here has the following structure: p + GaAs substrate / 200 nm p-Al 0.3 Ga 0.7 As (2 × 10 18 cm −3 ) / 100 nm p-GaAs (2 × 10 18 cm −3 ) / 60 nm n-Al x Ga 1−x As (1 × 10 17 cm −3 ) / 30 nm n-Al x Ga 1−x As (1 × 10 18 cm −3 ) / 9 nm n-GaAs (9 × 10 18 cm −3 ) / 20 nm Ga 0.92 Mn 0.08 As, i.e., the spin-LED from Ref. 4. In this structure, the Al-concentration in the spin-drift region is engineered together with the doping concentration in order to provide an effective barrier for the holes, such that carrier generation due to impact ionization is eliminated at low bias.…”