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

Abstract

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 ( Φ b , o = 0.80 eV ) obtained from the I– V characteristic is lower than the barrier height ( Φ b , o = 1.19 eV ) obtained from the C– V characteristic. The discrepancy between Φ b , o ( I – V ) and Φ 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- E v) to (0.68- E v)eV. The interface state density N ss ranges from 3.84×10 14 cm −2 eV −1 in (0.32- E v)eV to 1×10 14 cm −2 eV −1 in (0.68- E v)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.