Investigation of schottky barrier of poly(phenyl azo methane thiophene) using current-voltage and impedance spectroscopy

Current-voltage, impedance spectroscopy and capacitance-voltage characteris tics have been carried out on indium tin oxide (ITO)/poly(phenyl azo methan e thiophene) (PPAT)/In schottky barrier device. In this device, injection a nd transport is expected to be dominated by holes. The conduction mechanism in low field region is ohmic whereas the space charge limited current theo ry with an exponential distribution of traps is in extremely good agreement with at higher voltage region. The characteristic energy (E-t) of the expo nential traps distribution is 0.13 eV from the valence band edge at room te mperature but this shifts towards the valence band edge with the increase i n temperature. Electrical impedance measurements on PPAT schottky barrier d iodes in the frequency range 40 Hz-100 kHz were also reported. The device h aving configuration ITO/PPAT/In display the schottky behaviour, which can b e modelled by a simple equivalent circuit of two RC elements in series. rep resenting a bulk and a junction region. Low frequency device capacitance sh ows a pronounced voltage dependence and from a detailed analysis, the ionis ed acceptor concentration, potential barrier height and width of depletion layer have been calculated and discussed in detail. (C) 2001 Elsevier Scien ce B.V. All rights reserved.