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

Abstract Molybdenum disulfide (MoS 2 ) 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 HfO 2 and Al 2 O 3 gate insulators up to 275 °C. At 175 °C, devices with HfO 2 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 HfO 2 . This mechanism overrides initial hysteresis, revealing a pathway to memory-like functionality enhanced by narrower voltage sweep ranges. In contrast, transistors gated with Al 2 O 3 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: Al 2 O 3 is better suited for logic devices, whereas HfO 2 counterparts can serve as active layers for memory components.