Electronic Structure and Schottky Barriers in Ferromagnet/Semiconductor Junctions
This work is inspired by recent experiments on room temperature
electrical spin injection from magnetic metals into GaAs.
In the most successful experiments, spin injection efficiencies of 2% at
room temperature and 30% at low temperature were achieved.
The role of intrinsic Schottky barriers in controlling
spin-dependent tunneling through the interface is crucial since the
barriers
significantly reduce the conductivity mismatch, which would otherwise
eliminate the possibility of spin injection almost entirely.
Since there is still a lot of uncertainty in the prospects for spin
injection from magnetic metals into semiconductors, we believe
that further progress in this field would benefit from materials-specific
calculations of interfaces of interest.
We calculate Schottky barrier heights, magnetization profiles,
spin polarization, charge distributions, potential profiles, and
equilibrium structures of such junctions. Namely, we are
concentrating on Fe/GaAs, Co/GaAs, MnAl/GaAs, and MnGa/GaAs interfaces.
This knowledge of the interface properties will help improve understanding
of the spin injection process and guide the direction of future research.
Current progress
Relaxation of the structure
- Denis O. Demchenko and Amy Y. Liu,
Electronic Structure and Schottky Barriers in Magnetic Junctions Fe/GaAs
[Pedagogical talk]
.
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Fe/GaAs interface has several different interface reconstructions, and can be
either As- or Ga-terminated. A simplest ideal model of the interface is shown
in the figure. For each interface model we perform relaxation of the structure
in order to find its equilibrium geometry. The properties of ideal and relaxed
models can be significantly different. For every relaxed model we then compute
a full range of electronic and magnetic properties.
Potential profiles (click to enlarge)
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An example of the electrostatic potential profile for the relaxed
As-terminated Fe/GaAs interface. Three dimensional data can be integrated over
the x-y plane in the unit cell. Information about the details of electrostatic
potential behavior across the interface is hidden in bulk-like oscillations
(green curve).
A macroscopic averaging technique allows one get rid of them and to
compute Schottky barrier heights from the potential line-up (black curve).
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Similar data can be obtained to estimate the charge and spin transfer
across the interface.
Publications
