Degradation mechanisms of organic ferroelectric field-effect transistors used as nonvolatile memory

Abstract

Organic ferroelectric field-effect transistors were fabricated by inkjet printing for use as nonvolatile memory. Changes in device hysteresis were measured for 7 days to determine the limiting properties that restrict memory retention time. It was found that shifts in threshold voltage contributed to ∼55% of the reduction in transistor current, while decreased dielectric capacitance and reduced semiconductor mobility accounted for ∼30% and ∼15% of the current decay, respectively. The decrease in mobility and the shifts in threshold voltages are caused by remnant dipolar alignment in the ferroelectric insulator, and the reduction in gate capacitance is explained by injected charges in the ferroelectric dielectric. A method to calibrate and extract the input switching voltage is presented, and this calibration accounts for variations in device characteristics with time and allows the ferroelectric transistors to be used as analog memories.