Bandgap-Engineered Side-Path Synaptic Device Utilizing High-κ Materials for Low-Power Operation

This study proposes a method to optimize the charge transfer mechanism in synaptic devices, a practical core component of neuromorphic systems, by employing bandgap engineering (BE) with high-k materials. The conventional Al₂O₃ blocking oxide was substituted with a single HfO₂ layer and a stacked HfO₂/Al₂O₃ structure to enhance the program and erase characteristics. Simulation results indicate that the structures utilizing high- k materials demonstrated a larger threshold voltage (V_th) shift during program operations compared with the conventional structure. This improvement is attributed to the increased electron acceleration and the reduction in equivalent oxide thickness (EOT) due to the high permittivity of high-k materials. Moreover, a greater V_th shift was documented during erase operations, which is explained by the band offset between the blocking oxide and the nitride trap layer. Consequently, the BE charge-trap flash device demonstrated an enhancement of 2.22 V in the memory window compared with device in the conventional structure.