Defects Induced Charge Trapping/Detrapping and Hysteresis Phenomenon in MoS₂ Field-Effect Transistors: Mechanism Revealed by Anharmonic Marcus Charge Transfer Theory

Abstract

One critical problem inhibiting the application of MoS 2 field-effect transistors (FETs) is the hysteresis in their transfer characteristics, which is typically associated with charge trapping (CT) and charge detrapping (CDT) induced by atomic defects at the MoS 2 −dielectric interface. Here, we propose a novel atomistic framework to simulate electronic processes across the MoS 2 −SiO 2 interface, demonstrating the distinct CT/CDT behavior of different types of atomic defects and further revealing the defect type(s) that most likely cause hysteresis. An anharmonic approximation of the classical Marcus theory is developed and combined with state-of-the-art density functional theory to calculate the gate bias-dependent CT/CDT rates. All the key electronic quantities are calculated with Heyd−Scuseria−Ernzerhof hybrid functionals. The results show that single Si-dangling bond defects are active electron trapping centers. Single O-dangling bond defects are active hole trapping centers, which are more likely to be responsible for the hysteresis phenomenon due to their significant CT rate and apparent threshold voltage shift. In contrast, double Si-dangling bond defects are not active trap centers. These findings provide fundamental physical insights for understanding the hysteresis behavior of MoS 2 FETs and provide vital support for understanding and solving the reliability of nanoscale devices.

High Responsivity in Monolayer MoS2 Photodetector via Controlled Interfacial Carrier Trapping

“…25 For V GS > 0 V under dark conditions, the positive gate bias stress over a longer time (DC mode) enhances the electron trapping in both shallow and deep trap states originating from the MoS 2 /SiO 2 interface and intrinsic defects. 50 Rather, under illumination, the quasi-Fermi levels move apart and embrace few hole and electron traps; these trapped holes amplify the electron flow representing the PG effect, as shown in Figure 4b. According to previous reports, the deep-lying hole traps fill first and later on the shallow traps; it is worth mentioning that the shallow traps have shorter lifetimes, while the deep traps have a longer lifetime.…”

“…Upon illumination, the electron and hole density get temporarily enhanced, which is presented as the quasi-Fermi levels ( E f n′ , E f p′ ) . For V GS > 0 V under dark conditions, the positive gate bias stress over a longer time (DC mode) enhances the electron trapping in both shallow and deep trap states originating from the MoS 2 /SiO 2 interface and intrinsic defects . Rather, under illumination, the quasi-Fermi levels move apart and embrace few hole and electron traps; these trapped holes amplify the electron flow representing the PG effect, as shown in Figure b.…”

Ferroelectric-Gated All 2D Field-Effect Transistors with Sub-60 mV/dec Subthreshold Swing

“…The current ratio of the on/off state and carrier mobility were calculated as a function of V ds , indicating that a performance trade-off could be expected at a smaller V ds below 1 V to simultaneously obtain a high on/off ratio and carrier mobility (Figure b). Under ferroelectric polarization, a large current on/off ratio above 10 5 and a high electron mobility of up to 72.3 cm 2 /(V s) was obtained, which exceeded most MoS 2 -based transistors with conventional oxide gate dielectrics. , Besides, the values of the subthreshold swing (SS) were also calculated to be close to the physical limit (Figures c and d). It should be emphasized that the effective oxide thickness (EOT), which is the thickness of a layer of SiO 2 that would give an equivalent electrical performance as the higher constant dielectric layer being used, leads to a low leakage current.…”

Selective Enhancement of Photoresponse with Ferroelectric‐Controlled BP/In2Se3 vdW Heterojunction

“…The similar hysteresis loops can be attributed to the water molecules, oxide charge trapping, and surface charge trapping functioning as adsorbents. [34][35][36] Thus, to reduce the influence of these uncertainties, the measurement was performed in a vacuum environment at 1.8 × 10 −5 mbar. Furthermore, a 180°change in the piezoresponse phase (see Figure S7, Supporting Information) was observed owing to the reversal of the outof-plane (OOP) polarization of In 2 Se 3 under an external electric field.…”