Mobile charges in MoS₂/high-k oxide transistors: from abnormal instabilities to transient negative differential...

Molybdenum disulfide (MoS₂) field-effect transistors with high-k oxides lag behind silicon standards in stability due to traps causing clockwise hysteresis. While suppressing this effect is mandatory for logic devices, here we show an alternative strategy where initial hysteresis is dynamically overcome by stronger counterclockwise hysteresis coupled with memory-like transient negative differential resistance. We compare back-gated transistors using HfO₂ and Al₂O₃ gate insulators up to 275 °C. At 175 °C, devices with HfO₂ exhibit dominant counterclockwise dynamics and transient negative differential resistance. Our compact model suggests this behavior is caused by the drift of mobile oxygen vacancies within HfO₂. This mechanism overrides initial hysteresis, revealing a pathway to memory-like functionality enhanced by narrower voltage sweep ranges. In contrast, transistors gated with Al₂O₃ display only minor counterclockwise dynamics even at 275 °C due to higher vacancy migration barriers, maintaining superior stability. Our results reveal an insulator selection paradigm: Al₂O₃ is better suited for logic devices, whereas HfO₂ counterparts can serve as active layers for memory components.