Frequency and Voltage Dependence of the Capacitance of MIS Structures Fabricated With Polymeric Materials

In this paper, we present the frequency and voltage dependence of the capacitance in metal-insulator-semiconductor (MIS) structures fabricated with polymethyl-methacrylate (PMMA), as dielectric and three semiconductor polymers: poly(3-hexylthiophene), poly [N-9”-hepta-decanyl-2, 7-carbazole-ALT-5, 5-(4´ 7´ di-2-thienyl-2´ 1´ 3´ benzothiadiazole)], and poly[(9, 9-dioctylfluorenyl-2, 7-diyl)-CO-bithiophene]. It is shown that the dielectric constant of PMMA varies in the frequency range <; 1 MHz. In addition, the effect of the not yet depleted semiconductor can become important even in relatively thin layers and the presence of series resistance at the contacts can significantly modify the behavior of the capacitance-voltage (CV) curves. The calculated CV curves, in which specific material and interface properties are taken into account, are compared with the measured ones to identify the effects that determine the behavior of the capacitance with voltage and frequency for each analyzed MIS structure.