Non-volatile flash memory based on Van der Waals gate stack using bandgap tunability of hexagonal boron nitride

Electronic devices based on two-dimensional (2D) materials have extended their applications to non-volatile flash memory devices. The gate stack is a key structure in flash memory devices, and the conventional silicon-oxide-nitride-oxide-silicon (SONOS) structure has been widely applied. In this study, we propose a van der Waals (vdW) gate stack based on graphene, molybdenum disulfide (MoS₂), and hexagonal boron nitride (hBN) for next-generation flash memory devices. Owing to the bandgap tunability of hBN by functionalization, hBN is capable of forming a tunneling layer, charge trap layer, and blocking layer with different bandgaps, resulting in a suitable energy band offset for program/erase operations and charge storage. This study on the vdW gate stack of MoS₂/tunneling hBN/charge trap hBN/blocking hBN/graphene was carried out through technology computer-aided design (TCAD) simulation. The trapped charge density and threshold voltage (V_th) shift were investigated for different bandgaps of the hBN layers. Moreover, the pulse width and cycle were varied to reveal the charge-trapping behavior for further applications.