Neuromorphic synaptic applications of HfAlOx-based ferroelectric tunnel junction annealed at high temperatures to achieve high polarization

Abstract

HfO2-based ferroelectric tunnel junctions (FTJs) are promising nonvolatile memory types for neural network applications because of their speed, low power, and excellent complementary metal-oxide semiconductor compatibility. Specifically, HfAlOx (HAO) has led to extensive research efforts owing to its outstanding ferroelectric performance. This is a result of the fact that the atomic radius of Al is smaller than that of Hf. In this study, we investigate the metal–ferroelectric–semiconductor device with an Al doping concentration of 2% that was annealed at 900 °C. A high-remnant polarization (Pr) value of 39.85 µC/cm2 and endurance were achieved by using the polarization switching positive-up-negative-down measurement method at this annealing condition. Our device shows long-term potentiation and depression properties, including high linearity and multiple conductance states for neuromorphic applications. Moreover, paired-pulse facilitation was implemented to mimic human synaptic functions. The construction of 16 states comprising four bits was achieved by employing reservoir computing with the FTJ device functioning as a physical reservoir. Finally, the results obtained from the experiment show promising outcomes for the ferroelectric memory characteristics and synaptic properties of the manufactured HAO device.