Subject Area A3: Epitaxial Ferromagnet-Semiconductor Contacts
Wolfgang Hansen, Christian Heyn
This subject area deals with hybrid structures consisting of ferromagnets and modulation-doped semiconductor
heterostructures. Ferromagnetic metals, in particular Heusler alloys, possess electron systems with a high
degree of spin polarization. For spintronic devices it is important to achieve a high spin-injection rate
from the ferromagnet into the low-dimensional electron system of a semiconductor. The quality of the interfaces
is crucial for polarized spin injection. Therefore we plan to epitaxially grow metallic layers on semiconductor
heterostructures. The hybrid structures will be fabricated in an ultra-high vacuum cluster of semiconductor-
and metal-deposition chambers. With this facility it is possible to deposit the metallic layer directly
after the semiconductor growth without contact to air.
Transfer line of the vacuum cluster combining semiconductor and metallic-layer growth facilities.
Concretely, we plan the epitaxial growth of iron and the Heusler
alloys Ni2MnIn, Ni2MnGa and Ni2MnGe on semiconductor heterostructures.
With molecular-beam epitaxy we are able to grow ultra-clean GaAs/AlGaAs and various InAs heterostructures
with high electron mobilities. The composition of the metallic layers, intermixing effects, and the formation
of dislocations will be studied in situ by Auger electron spectroscopy (AES) and
low-energy electron diffraction (LEED). Further characterizations will be performed ex situ by
atomic-force microscopy, magnetic-force microscopy, X-ray diffraction and transmission electron microscopy.
The spin polarization will be determined by point-contact Andreev spectroscopy.
"Hybrid semiconductor/metal nanostructures with two-dimensional electron systems"
Superlattices and Microstructures 33, 357-367 (2004).
S. Löhr, Ch. Heyn, and W. Hansen
"Nonplanar two-dimensional electron gases in InAs heterostructures on GaAs"
Appl. Phys. Lett. 84, 550-552 (2004).
A. Zolotaryov, A. Volland, Ch. Heyn, D. Novikov, G. Stryganyuk, A. Kornowski, T. Vossmeyer,
O. Albrecht, E. Coric, and W. Hansen
"Influence of growth temperature on phase and intermixing in Heusler Ni2MnIn films on InAs(001)",
Journal of Crystal Growth 311, 2397-2404 (2009).
Molecular-beam epitaxy of Heusler alloys on InAs heterostructures
Spin-polarized tunnneling through epitaxial ferromagnet-semiconductor contacts in non-local geometry