Magnetic and electrical characterization of “ferromagnet/insulator/silicon” diodes

This work is focused on the study of magnetic and electrical properties of ferromagnet/semiconductor heterostructures that can be used for spin injection into silicon. Three different studies are conducted whose principal results will be presented. In all these studies, a simple diode-like ferromagnet/insulator/semiconductor (FM/I/S) structure is used. The first study aimed to investigate whether a magnetic “dead” layer is obtained at the ferromagnet/oxide barrier that could lead to spin depolarization of the injected electrons. The results show the absence of such layer even after annealing at temperatures up to 723 K (450 °C). The second study focused on the mechanisms of electrical transport through the insulator barrier. Capacitance–voltage as well as current–voltage characteristics have been measured. The results underline the importance of controlling the ferromagnet deposition process in obtaining defect-free silicon–insulator interface, a prerequisite to spin conservative direct-tunnel transport process. In the third study, magnetic characterization of diodes that may be used for spin injection and collection were performed.