The investigation of electrical and dielectric properties of metal-polymer-semiconductor (MPS) structures in the wide frequency range

The energy density distribution profile of the interface states (Nss) and their relaxation time (?) and capture cross section (?p) of metal-polymer-semiconductor (Au/PVC+TCNQ/p-Si) structures have been investigated by use high-low frequency capacitance (CHF-CLF) and conductance method. The value of capasitance C in the Au/PVC+TCNQ/p-Si structures increases with decreasing frequency as almost exponentially due to the presence of (Nss) at metal/semiconductor M/S interface. The energy distributions of the Nss and?? have been determined in the energy range of (0.053-Ev)-(0.785-Ev) eV by taking into account the surface potential as a function of applied bias voltage. The value of Nss ranges from 3.88x1012 eV-1cm-2 to 3.24x1012 eV-1cm-2. In the same energy interval, the value of ? ranges from 5.73x10-5 s to 1.58x10-4 s. The obtained Nss values from CHF-CLF and conductance methods are good agreement each other for Au/PVC+TCNQ/p-Si heterojunction. As a result, the mean value of Nss was found 1012 eV-1cm-2 order and this value is very suitable for an electronic device. Dielectric constant (??, ???), loss tangent (tan?), and the real and imaginary parts of the electric modulus (M?, M??) and ?ac values of this structure has been investigated in the wide frequency range of 1 kHz-5MHz at room temperature for Au/PVC+TCNQ/p-Si structure. All of these values were found strongly as function of frequency and voltage especially in the inversion and depletion regions at low frequencies due to interfacial polarization and charges at interface states (Nss). The decrease in ?? and ??? with increasing frequency indicated that the interfacial dipoles have less time to orient themselves in the direction of the alternate field. While the value of M? increase with increasing frequency and reach a maximum, M?? shows a peak and the peak position shifts to higher frequency with increasing applied voltage. The ln(?ac) vs ln(?) plot of the structure for 0.5 V has three linear regions (I, II and III) with different slopes which are corresponding to low, intermediate and high frequency ranges, respectively. Such behavior of ln(?ac) vs ln(?) plot indicated that there are three different conduction mechanisms in the Au/PVC+TCNQ/p-Si structure at room temperature.