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 (Φb,o=0.80eV) obtained from the I–V   characteristic is lower than the barrier height (Φb,o=1.19eV) obtained from the C–V   characteristic. The discrepancy between Φb,o(I–V)Φb,o(I–V) and Φb,o(C–V)Φb,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.