Solution processed Li-Al2O3/LiNbO3/Li-Al2O3 stacked gate dielectric for a non-volatile ferroelectric thin film transistor

Abstract

Lithium niobate (LiNbO3) gate dielectric based SnO2 ferroelectric thin film transistor (FETFT) is fabricated by a simple solution processed technique. However, LiNbO3 alone is not a suitable candidate for a gate insulator of a TFT because of its low band gap. Therefore, Li-Al2O3/LiNbO3/Li-Al2O3 stacked gate dielectric has been used that reduces the gate leakage current by an order of magnitude compared to the LiNbO3 only device. Moreover, ionic polarization of Li-Al2O3 thin films that originated from mobile Li+ of Li-Al2O3, compensate for the ferroelectric charge polarization of LiNbO3 film. By reducing gate leakage current and compensating ferroelectric charge polarization, it becomes possible to achieve ferroelectric memory retention up to 7.2× 103 s of time with a difference of ON/OFF state by 3 times whereas the reference LiNbO3 device almost merges to each other very quickly. Besides, these ferroelectric TFTs (FETFT) can operate within 2 V operating voltage due to the strong ionic polarization of the gate dielectric. The carrier mobility of 1.9 cm2. V−1.s−1, current ON/OFF ratio of 1.6⨭104 and subthreshold swing (SS) of 167 mV.decade−1 has been achieved under 2 V operation of this FETFT, whereas memory retention time has been studied at 0 V gate and 1 V drain bias.