On the form of high-frequency voltage-capacitance characteristics of metal-insulator-semiconductor structures with a ferroelectric insulating layer BaxSr1-хTiO3

Abstract

A model of the high-frequency impedance of metal-ferroelectric-semiconductor structures has been composed and analyzed. An algorithm is formulated for recovering the impedance of the potential drop across the ferroelectric layer, band bending in a semiconductor, the total concentration of charged boundary states and minority charge carriers on the semiconductor surface from the experimental field characteristics as a function of the voltage across the structure. The results of high-frequency measurements of the capacitance and conductivity of Ni–Ba0.8Sr0.2TiO3–Pt and Ni–Ba0.8Sr0.2TiO3–Si structures in the paraelectric phase are presented. It is shown that Si does not evolve into a state of strong depletion in the entire range of external voltages, and the capacitances of the semiconductor and the metal-ferroelectric-silicon structures practically coincide. This is due to the almost complete screening of the ferroelectric layer polarization by the charges of electron traps at the Ba0.8Sr0.2TiO3–Si contact. It is proposed to use dangling bond passivation methods realized in planar silicon technology to reduce the concentration of active trapping centers at the ferroelectric-semiconductor interface.