Electrical and impedance spectral characterisation of ITO/DAG/In device

Abstract

A Schottky device, with configuration ITO/DAG/In is fabricated using diazopheny diamino glyoxime (DAG) as an n-type organic material. Current–voltage characteristics and impedance spectroscopy measurements were carried out, which reveals that the injection and transport properties are dominated by negative charge carriers. Space charge limited current theory with an exponential distribution of traps is very well followed by observations resulted through current–voltage characteristics at high voltage region. This gives a traps density N t of about 4.5×10 21 m −3 and mobility of electron is about 3.9×10 −10 m 2 V −1 s −1. It is found that DAG behaves as an n-type materials as it forms Schottky barrier with ITO (high work function electrode) and conduction is governed by majority carriers, i.e. electrons. Using temperature and bias dependence of impedance spectral characteristics in a broad frequency range, i.e. 40 Hz to 100 kHz, it is found that the ac behaviour of In/DAG/ITO device shows several features, described by the simple double RC circuit representing a depleted junction region and an undepleted bulk region. From the large frequency range of impedance spectroscopy two distinct processes were identified, corresponding to bulk DAG layer and junction region. The activation energy of the relaxation times coincides well with the results obtained from the temperature dependent dc conductivity. The temperature dependent capacitance–voltage measurements were analysed at a frequency of 40 Hz. The obtained inherent donor concentration from 1/ C 2– V plots varies from 1.8×10 23 m −3 at room temperature to 5.9×10 23 m −3 at 360 K.