Ge N-Channel Ferroelectric FET Memory With Al2O3/AlN Interfacial Layer by Microwave Annealing

Abstract

While n-FeFET memory devices have shown promising characteristics for data storage and neuromorphic computing, implementing such devices with a Ge channel, which is expected to be adopted in advanced technology nodes, has never been reported due to the challenges in achieving desirable Ge interface quality. In this work, ferroelectric HfZrO_x (HZO) is integrated with a high-k Al₂O₃/AlN interfacial layer (IL), along with microwave annealing (MWA), to implement Ge n-FeFET memory devices, and their memory and reliability characteristics, as well as their potential for neuromorphic applications, are extensively explored. A large memory window (MW) of 2.5 V is achieved by applying ±5 V for 5 µs while 3 bits/cell (triple-level cell) operation is demonstrated. By using a recovery scheme, excellent 1-bit/cell (single-level cell) characteristics up to 10⁸ cycles are also obtained. The proposed IL and low thermal budget of MWA alleviate element diffusion and reduce oxygen vacancies, marking the first demonstration of Ge n-FeFET memory devices controlled by dipoles. Furthermore, short-term synaptic plasticity, such as excitatory/inhibitory postsynaptic currents (EPSC/IPSC), which are essential for neuromorphic computing is also achieved. These findings suggest that Ge n-FeFET memory devices could pave the way for high-density embedded memory applications and could further be integrated with existing Ge p-FeFET memory devices to form Ge-based FeCMOS, enabling more versatile circuit functionalities.