Recently, the organic spintronics has been an intensive investigated field in condensed matter physics. How to achieve effective spin injection from electrode material to the organic spin transport layer is still one of the issues attracting much interest. GaMnAs, an inorganic ferromagnetic semiconductor, which provides highly spin polarized holes in its valence band and better resistance match with organic semiconductors, is a good candidate for hole spin polarized injection electrode....[ Read more ]

Recently, the organic spintronics has been an intensive investigated field in condensed matter physics. How to achieve effective spin injection from electrode material to the organic spin transport layer is still one of the issues attracting much interest. GaMnAs, an inorganic ferromagnetic semiconductor, which provides highly spin polarized holes in its valence band and better resistance match with organic semiconductors, is a good candidate for hole spin polarized injection electrode.

In this thesis, GaMnAs and a prototypical organic hole transport semiconductor NPB hybrid structure is studied, with the main focus on the interface electronic property, including the band alignment and interface dipole formation. This work will serve as a starting point for the application of GaMnAs in organic spintronics.

Hole only devices with GaMnAs/NPB/Al structure were successfully fabricated, and the current density – voltage (J-V) curves were measured. Simulations performed on this device structure yielded the hole injection barrier between GaMnAs and NPB to be 0.77 eV. A vacuum level shift at GaMnAs/NPB interface is deduced as 0.54 eV. These results agree well with the results from ultraviolet photoemission spectroscopy (UPS), namely 0.79 eV for the valence band and the HOMO band offset and 0.53 eV for the vacuum level shift. The interface dipole formation is attributed to the charge transfer across GaMnAs and NPB interface states. Temperature dependent J-V curves also provide consistent results indicating the center position of NPB HOMO to be approximately 1.16 eV below GaMnAs valence band edge.