Interface dipole formation between GaMnAs and organic material

The interface band alignment between GaMnAs and organic material was investigated by current transport measurement in hole only devices with GaMnAs/NPB/Al structure. The current density – voltage (J-V) curves were measured and numerical 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 was deduced as 0.54 eV, indicating a dipole layer across the interface. We attributed the vacuum level shift to the charge transfer across the interface.