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

Abstract

In this study, we demonstrate that a room-temperature reactively sputtered aluminum oxynitride (AlOxNy) overlayer enables both effective doping and pronounced threshold voltage hysteresis in multilayer MoS2 FETs, while preserving field-effect mobility. Compared to conventional AlOx , the AlO x N y layer introduces trap states that are energetically aligned with the conduction band of MoS2, 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 similar to 250 K, which correlates with the activation of out-of-plane phonon modes in MoS2. These phonons are proposed to assist in activating interfacial trap states within the AlOxNy 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 AlOxNy as a low-temperature-processable dielectric for 2D FETs and advance a new perspective on phonon-assisted interfacial charge modulation.