Admittance of Pentacene- Based Mis-Structures with Two-Layer Insulator SiO2-Al2O3

Experimental studies of the admittance of MIS structures based on pentacene with a two-layer insulator SiO2-Al2O3 and back contacts made of various materials (Au, Al, In, and Ag) have been carried out in a wide range of frequencies, temperatures, and biases. The concentration of holes in the organic pentacene film found from the capacitance-voltage characteristics took rather high values (in the range (4-40) center dot 10(17) cm(-3)). The magnitude of the hysteresis of electrophysical characteristics turned out to be minimal for structures with Ag and In back contacts. Significant hysteresis was found for structures with back contacts made of Au and Al at 300 K. For the structure with an Al back contact, a maximum capacitance was observed at the forward voltage sweep in weak accumulation mode, which can be associated with the recharge of the surface state level 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 equivalent circuit elements are found at various biases and temperatures. For structures with back contacts made of Au and Ag, maxima in the temperature dependences of the conductivity associated with the recharge of bulk traps in the organic pentacene film were found.

Automated summary

Experimental studies were conducted on the admittance of MIS structures based on pentacene with different back contacts and insulator materials. The concentration of holes in the pentacene film was found to be high, with minimal hysteresis for structures with Ag and In back contacts. The equivalent circuit of the pentacene-based MIS structure was proposed to analyze impedance frequency dependences under various conditions, with maxima in the temperature dependences of conductivity for structures with Au and Ag back contacts.