Experimental studies of the admittance of MIS structures based on pentacene with a two-layer dielectric SiO2-Al2O3 and various materials for backward contact (Au, Al, In, Ag) have been carried out in a wide range of frequencies, temperatures, and biases. The concentration of holes in the organic film of pentacene, found from the capacitance-voltage characteristics, took rather high values (in the range (4-40)×1017 cm-3). The magnitude of the hysteresis of the electrophysical characteristics turned out to be minimal for structures with Ag and In reverse contacts. Significant hysteresis was found for structures with reverse contacts made of Au and Al at 300 K. For a structure with a reverse contact made of Al, with a forward voltage sweep in a weak accumulation mode, a maximum capacitance was observed, which can be associated with a recharge of the level of surface states at the interface between the inorganic insulator and pentacene. An equivalent circuit of a pentacene-based MIS structure is proposed, which allows one to calculate the frequency dependences of the impedance under various conditions. The values of the elements of the equivalent circuit are found at various biases and temperatures. For structures with backward contacts made of Au and Ag, maxima on the temperature dependence of the conductance associated with the recharge of bulk traps in the organic pentacene film were found.
Investigation of the Voltage Dependent Surface States and Their Relaxation Time of the Al/CdZnO/p-Si (MIS) Structure Via Admittance Method
