Electrophysical Characteristics of the Pentacene-based MIS Structures with a SiO2 Insulator

Abstract

In a wide range of frequencies and temperatures, the admittance of MIS structures based on pentacene organic films, formed by thermal evaporation in vacuum on SiO₂ and SiO₂/Ga₂O₃ substrates, was experimentally investigated. The capacitance-voltage characteristics of MIS structures with a SiO₂ insulator have virtually no hysteresis. It is shown that at temperatures of 150–300 K, an inversion layer is formed in the structures at large positive bias voltages. The concentration of holes in pentacene, determined from the capacitive measurements, exceeds 10¹⁸ cm^–3 and is practically independent of temperature and frequency. The experimental frequency dependences of the admittance of MIS structures with the SiO₂ insulator are in good agreement with the results of calculations performed using the method of equivalent circuits. For structures with a Ga₂O₃ layer, the negative differential conductance of the insulating layer was detected, which requires the complication of the equivalent circuit. The possibility of using the low-temperature admittance measurements for studying the traps in the pentacene film bulk is shown.