Hybrid Epitaxial Structures for Spintronics
INTERUNIVERSITY MICRO-ELECTRONICS CENTER LOUVAIN (BELGIUM)
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Molecular beam epitaxy MBE has been used very successfully over the past 10 years to produce the most interesting spintronic heterostructures. This paper illustrates the strength of MBE in realizing materials combinations that can lead to efficient spin-injection. The paper is not an exhaustive description of all possible materials combinations, but a review of some important aspects of spin-source fabrication. In line with todays emphasis on demonstrating the spin-injection process in III-V electroluminescent semiconductor devices, the paper will focus on Gallium Arsenide-based GaAs-based epitaxial heterostructures. The first part of the paper describes the epitaxy of metallic ferromagnetic elements and alloys on GaAs. The authors review the results of initial experiments on Iron Fe and Cobalt Co epitaxy, since these materials are in the picture for Schottky barrier spin-injection devices today. Further, a brief description of Manganese-based Mn alloys is presented, justified by the wealth of possible Mn-III or Mn-V alloys that can be epitaxially grown on GaAs with various properties. This section is followed by a discussion of Gallium Manganese Arsenide GaMnAs as a ferromagnetic semiconductor and a summary of the results obtained recently on the epitaxial growth of Nickel Manganese Antimony NiMnSb on GaAs, a half-metallic magnetic alloy that has the potential to serve as a spin-source with 100 spin-polarization. The authors also briefly discuss some results on the realization of heterostructures, including two magnetic layers spaced by a semiconductor or vice versa. A very appealing class of materials for spintronics is that of magnetic semiconductors, illustrated in this paper by Aluminum,Gallium Manganese Arsenides Al,GaMnAs. A concluding section deals with the contact strategies ohmic, Schottky barrier, or tunnel barrier for spin-injection reports in which the materials combinations play an important role. 9 figures, 94 refs.
- Electricity and Magnetism
- Solid State Physics