Epitaxial PZT Film-Based Ferroelectric Field-Effect Transistors for Artificial Synapse

Neuromorphic computing systems that mimic the human brainhaverecently attracted substantial attention because they allow for theefficient processing of large amounts of data. These systems are composedof neurons and synapses to transfer information; synapses play a particularlyimportant role in transmitting and integrating processed signals betweenthe neurons. The ferroelectric field-effect transistors (FeFETs) canmeet the required properties of artificial synaptic devices becausethe channel current can be controlled with changes in applied gatevoltage due to two stable polarization states, meaning that the datacan be memorized in various states. In this study, the epitaxial Pb(Zr0.20Ti0.80)O-3 (PZT) film was grown onLa(0.67)Sr(0.33)MnO(3) (LSMO) bufferedSrTiO(3) (STO) single crystal substrate using pulsed laserdeposition (PLD). As the channel layer, the amorphous indium galliumzinc oxide (a-IGZO) was employed due to its large carrier mobilityand good uniformity. The epitaxially grown single-crystal PZT thinfilm has a residual polarization (P (r))value of 20.2 & mu;C/cm(2) and the a-IGZO thin film transistorhas a carrier mobility of 10.23 cm(2)/V s. The biologicalsynaptic behaviors were emulated using the fabricated FeFETs basedon the PZT and a-IGZO thin film as a gate insulator and channel material,respectively. The synaptic plasticity was analyzed according to theapplied voltage pulse condition. The calculated nonlinearity valueswere 0.00 and 5.41 with 16 pulse numbers and 0.51 and 7.05 with 32pulse numbers for potentiation and depression, respectively.