Non-Volatile Field-Effect Transistors Enabled by Oxygen Vacancy-Related Dipoles for Memory and Synapse Applications

Exploring the high-performance non-volatile memories for realizing energy-efficient memory in complementary metal-oxide-semiconductor (CMOS) circuits, memory-in-computing, and the artificial synapse is the key to the rapid growth in data markets. One of the significant aspects is the development of non-volatile field-effect transistor (NVFET), which possesses the advantage of decoupling the 'write' and 'read' functions using the third terminal. In this work, building on a semiconductor channel integrated with an amorphous Al₂O₃ gate insulator, we report a ferroelectric-like NVFET memory and analog synapse that differ from those utilizing polycrystalline-doped HfO2 films. Switchable polarization ( ${P}$ ) is demonstrated in TaN/Al2O3/TaN, TaN/Al2O3/Si, and TaN/Al2O3/Ge stacks, which is attributed to the voltage-modulation of the oxygen vacancy and negative charge dipoles in gate insulator. A TaN/Al2O3/Ge capacitor achieves over 1010 cycles endurance of polarization-voltage measurement. A memory window (MW) of 0.85 V is obtained in the NVFET integrated with Al2O3 insulator under ±3 V at 100 ns program/erase (P/E) condition, and the P/E voltage can be reduced to ±1.6 V. A NVFET analog synapse is demonstrated to have a dynamic range above 100 [asymmetry ( $\vert \alpha _{p} - \alpha _{d} \vert $ )< 0.1] with ±2 V/100 ns potentiation/depression pulses. These results can be extended universally to other amorphous oxides and show promise for 3-D (fin-shaped) NVFETs with very small fin pitch.