Electrical characterization of Al/MEH-PPV/p-Si Schottky diode by current-voltage and capacitance-voltage methods

The electrical characterization of the Al/poly[2-methoxy-5-(2?-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV)/p-Si structure has been investigated by current-voltage and capacitance-voltage methods. The Al/MEH-PPV/p-Si Schottky diode with the ideality factor value of 1.88 obeys a metal-interfacial layer-semiconductor (MIS) configuration rather than an ideal Schottky diode due to the existence of an insulating layer on the organic semiconductor. The barrier height (?b, o = 0.80 eV) obtained from the I-V characteristic is lower than the barrier height (?b, o = 1.19 eV) obtained from the C-V characteristic. The discrepancy between ?b, o (I - V) and ?b, o (C - V) can be due to the existence of the interfacial native oxide and the organic MEH-PPV layers between the semiconductor and Schottky contact metal. The barrier height value for the Al/MEH-PPV film/p-Si/Al contact obtained at the room temperature that is significantly larger than that for the conventional Al/p-Si Schottky diode. The density distribution curves of the interface states is in the range (0.32-Ev) to (0.68-Ev)eV. The interface state density Nss ranges from 3.84×1014 cm-2 eV-1 in (0.32-Ev)eV to 1×1014 cm-2 eV-1 in (0.68-Ev)eV, of the Al/MEH-PPV/p-Si. The interface state density has an exponential rise with bias from the midgap towards the top of the valence band of the p-Si.