Nb-doped Gd₂O₃ as charge-trapping layer for nonvolatile memory applications

The charge-trapping properties of Gd₂O₃ with different Nb doping levels are investigated using an Al/Al₂O₃/Gd₂O₃/SiO₂/Si structure. Compared with the memory device with pure Gd₂O₃, the one with lightly Nb-doped Gd₂O₃ shows better charge-trapping characteristics, including higher programming speed (6.5 V at +12 V programming voltage for 10 ms) and better retention property (92% retained charge at 85 °C after 10⁴ s), due to its higher trapping efficiency that resulted from higher trap density and suppressed formation of a silicate interlayer at the Gd₂O₃/SiO₂ interface induced by the Nb doping. Moreover, the one with heavily Nb-doped Gd₂O₃ shows improvement in erasing behavior but worse retention and lower programming speed than the one with lightly Nb-doped Gd₂O₃. Further analysis reveals that the Nb-doping level determines the type of dominant trap in the Nb-doped Gd₂O₃, thus leading to different charge-loss mechanisms and charge-trapping characteristics.