Phonon-Assisted Charge Trapping and Threshold Voltage Modulation in MoS₂ FETs with AlO_xN_y Overlayers

In this study, we demonstrate that a room-temperature reactively sputtered aluminum oxynitride (AlO x N y ) overlayer enables both effective doping and pronounced threshold voltage hysteresis in multilayer MoS 2 FETs, while preserving field-effect mobility. Compared to conventional AlO x, the AlO x N y layer introduces trap states that are energetically aligned with the conduction band of MoS 2, facilitating charge exchange across the heterointerface. Capacitance–voltage measurements confirm that nitrogen incorporation reduces the effective fixed charge density, enabling mobility-preserving operation without thermal annealing. Notably, the hysteresis window exhibits a marked expansion above ∼250 K, which correlates with the activation of out-of-plane phonon modes in MoS 2 . These phonons are proposed to assist in activating interfacial trap states within the AlO x N y layer, as supported by temperature-dependent electrical and spectroscopic analyses. While such trap-induced hysteresis may be undesirable for logic circuits, it offers valuable functionality for emerging device architectures─such as in-memory computing and neuromorphic systems─where hysteresis can be exploited. These findings underscore the potential of AlO x N y as a low-temperature-processable dielectric for 2D FETs and advance a new perspective on phonon-assisted interfacial charge modulation.