Thickness-engineered polarization-like switching and charge-storage behaviour in PLD-grown Mg-doped ZnO MIS capacitors for non-volatile memory applications

Abstract Mg-doped ZnO (Zn 0.85 Mg 0.15 O) thin films with thicknesses of 20, 50, and 100 nm were deposited on n-type Si (100) substrates by pulsed laser deposition and evaluated in Au/MgZnO/Si metal–insulator–semiconductor (MIS) capacitor structures for non-volatile memory behaviour. X-ray diffraction confirms single-phase wurtzite structure with successful Mg incorporation and thickness-dependent crystallinity improvement. Optical analysis reveals band-gap widening (3.35–3.42 eV) consistent with Mg substitution. Electrical measurements demonstrate pronounced thickness-dependent device performance. The 20 nm film exhibits elevated leakage current (∼10 −3 A) and high interface trap density (∼10 11 eV −1 cm −2 ), while the 100 nm film shows improved dielectric stability but reduced electric-field coupling. The optimized 50 nm film achieves the best balance, exhibiting a stable C–V memory window of 2.05 V at ±5 V, moderate interface trap density (∼10 10 eV −1 cm −2 ), and reversible polarization-like switching with remnant polarization of 0.28 μC cm −2 . Endurance up to 3000 cycles and retention stability over 3000 s demonstrate minimal degradation of the memory window. These results show that thickness engineering enables controlled defect-mediated polarization-like switching and stable charge-trap behaviour in Mg-doped ZnO MIS capacitors, supporting their suitability as oxide-based non-volatile memory platforms.