Fabrication and characterization of a Magnetic Tunnel Transistor with an epitaxial spin valve by the shadow mask technique

摘要

This work is concerned with the development of a fabrication method for Magnetic Tunnel Transistor (MTT) having an epitaxial spin valve. Over the years, this device has been used for the study of spin polarized hot electron transport in thin films. Further, the high on/off ratio that the use of thin magnetic films enables makes this device interesting for industrial application. One of the main limitations of this device however is the low ratio between the injected current and the collected current. In this work, use of epitaxial layers has been made so as to decrease the scattering probability of hot electrons, thereby increasing the aforementioned ratio. In order to ensure a high fabrication throughput as well as reduce the amount of lithography induced defects, a shadow mask based deposition method has been successfully developed. This thesis first describes the theoretical framework of the spin polarized hot electron transport in the MTT and investigates using a Monte Carlo algorithm the influence of structural defects, bandstructure as well temperature on the different characteristic parameters of the MTT. The fabrication method is subsequently describes and finally the experimental results are discussed in light of the theoretical prediction of the model as well as of the previous experimental reports on MTTs.