Electrical spin injection in epitaxial ferromagnet／semiconductor hybrid structures

다국어 초록 (Multilingual Abstract)

The electrical spin injection and detection is observed in epitaxially grown Fe/GaAs hybrid structure. In hybrid spintronic devices such as spin-FETs (Spin-Field-Effect Transistors), it is important to inject spin-polarized electrons into semiconductor and then to detect these spins from semiconductor. The Schottky tunnel barrier which is formed at the interface of Fe/GaAs is used for efficient spin injection into semiconductor and subsequent spin detection. The hysteresis loop in Fe/GaAs thin film grown by MBE (Molecular Beam Epitaxy) is measured by AGM (Alternating Gradient Magnetometer). The result shows that Fe thin film grown on GaAs have a different anisotropic properties from bulk or film Fe.
Photolithography and etching (ion milling and reactive ion etching) technic are used for the spin injection device fabrication. The I-V characteristic in the interface between Fe and GaAs is investigated indirectly. AMR (Anisotropic Magneto Resistance) measurement is performed to get the coercive field of two Fe electrodes (spin injector and detector). In the same device non-local spin signal is measured for the evidence of spin injection and detection. The dips in non-local spin signal are nicely matched with the anti-parallel ranges of two Fe electrodes which are acquired by AMR measurement. The local spin valve signal is also measured in the other spin injection device.

목차 (Table of Contents)

• Abstract = 1
• List of figure captions = 3
• 1. Introduction = 7
• 2. Theoretical background = 10
• 3. Experiments = 15
• 3.1. Fe/GaAs hybrid structure = 15
• 3.2. Fabrication process = 20
• 3.3. Measurement = 27
• 4. Results and discussion = 30
• 4.1. Interface I-V characteristic = 30
• 4.2. AMR (Anisotropic Magneto Resistance) = 32
• 4.3. Non-local spin signal = 35
• 4.4. Local spin valve signal = 41
• 5. Conclusion = 45
• 6. References = 47