Capacitance-voltage characterization of polyfluorene-based metal-insulator-semiconductor diodes

Metal-insulator-semiconductor structures with conjugated polymer ethyl-hexyl substituted polyfluorene (PF2_6) as the active semiconductor layer, Al2O3 as the insulating oxide layer, and p(+)-Si as the metal layer have been characterized by means of capacitance-voltage (C-V) and conductance-voltage methods. The negative shift of the flat-band voltage with increasing frequency arises from positive interface charges in the PF2_6/Al2O3 layer. From C-V measurements the unintentional doping density is evaluated as similar to 5.7x10(17) cm(-3) at frequencies above 20 kHz. The interface trap density is estimated as similar to 7.7x10(11) eV(-1) cm(-2) at the flat-band voltage. (c) 2006 American Institute of Physics.