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Effects of Trapped Charges in Gate Dielectric and High-k Encapsulation on Performance of MoS? Transistor
摘要： The effects of trapped charges in gate dielectric and high-k encapsulation layer on the performance of MoS2 transistor are investigated by using SiO2 with different thicknesses as the gate dielectric and HfO2 as the encapsulation layer of the MoS2 surface. Results indicate that the positive trapped charges in SiO2 can increase the electrons in MoS2 for screening the scattering of charged impurity (CI) in SiO2 and at the SiO2/MoS2 interface to increase the carrier mobility. However, the CI scattering becomes stronger for thicker gate dielectric with more trapped charges and can dominate the electron screening effect to reduce the mobility. On the other hand, with the HfO2 encapsulation, the OFF-currents of the devices greatly increase and their threshold voltages shift negatively due to more electrons induced by more positive charges trapped in HfO2. Moreover, the screening effect of these electrons on the CI scattering results in a mobility increase, which increases with the magnitude of the CI scattering. A 51% improvement in mobility is obtained for the sample suffering from the strongest CI scattering, fully demonstrating the effective screening role of high-k dielectric on the CI scattering.
关键词： Charged impurity (CI) scattering,mobility,high-k encapsulation,trapped charges,MoS2 FET
更新于2025-09-23 15:22:29
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Performance analysis of a substrate-engineered monolayer MoS2 field-effect transistor
摘要： We investigate the impact of different substrates on the performance of a monolayer MoS2 field-effect transistor (FET) by calculating the interface charge density between the MoS2 layer and the substrate using first-principle calculations based on density functional theory to provide details about the overlap of electron orbitals at the interface. The electrical characteristics of the monolayer MoS2 FET are determined by using the extracted interface charge density in numerical simulations. The electron transport behavior of the monolayer MoS2 FET is modeled using the nonequilibrium Green’s function with mode space (NEGF_MS) approach. We study and compare the performance of monolayer MoS2 FETs on different substrates, viz. SiO2, HfSiO4, Si3N4, HfO2, and h-BN. The results reveal that the monolayer MoS2 FET on the h-BN/Si substrate exhibits an on-current of 548 μA/μm and a subthreshold swing of 65 mV/dec.
关键词： Carrier fluctuations,Electron transport,Charge density,NEGF_MS,Monolayer MoS2 FET
更新于2025-09-09 09:28:46
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Static and Dynamic Piezopotential Modulation in Piezo-Electret Gated MoS <sub/>2</sub> Field-Effect Transistor
摘要： The piezotronic effect links the mechanical stimuli with various semiconductor devices, promising for low-power-consuming electronic devices, sensitive sensors and interactive control system. The persistent requirement for external strains in piezotronic modulation may hinder its application in some circumstances (such as devices on rigid substrate, or complicated synergistic piezoelectric modulation on multi-device). Here, we propose an efficient method to realize piezoelectric modulation of optical and electrical properties of MoS2 FET in both static and dynamic manner, expanding the application of piezotronics. Through capacitive coupling between piezo-electret and MoS2 FET, the remanent piezo-potential can efficiently tune the Fermi level of MoS2, programming the initial electrical property for subsequent fabrication of sophisticated devices. The external strain can induce enhanced piezo-potentials to further affect the energy band bending of MoS2 channel, giving rise to high performance strain sensors (large gauge factor ~4800, fast response time ~0.15s and good durability >1000 s). The proposed static and dynamic piezopotential tuned MoS2 FET is easy to extend to devices based on other materials, which is highly desired in tunable sensory systems, active flexible electronics, and human-machine interface.
关键词： piezo-electret,optical and electric properties,mechanical sensors,MoS2 FET,piezopotential modulation
更新于2025-09-04 15:30:14
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Total-Ionizing-Dose Response of MoS2 Transistors with ZrO2 and h-BN Gate Dielectrics
摘要： The total-ionizing-dose response of few-layer MoS2 transistors with ZrO2 or h-BN gate dielectrics is investigated under various bias conditions. Defects in MoS2 and surrounding dielectric layers significantly affect radiation-induced trapping. For devices with ZrO2 dielectrics, much larger negative Vth shifts and peak transconductance degradation are observed for irradiation under negative and ground bias than under positive bias. h-BN devices exhibit positive threshold voltage shifts under negative-bias irradiation. For both ZrO2 and h-BN passivated devices, the peak transconductance degradation results from charge trapping at the surface of the MoS2 or in nearby oxides. Changes in defect energy distributions of MoS2 FETs during X-ray irradiation are characterized via temperature-dependent low-frequency noise measurements. Density functional theory calculations are performed to provide insight into the pertinent defects.
关键词： DFT,MoS2 FET,low frequency noise,ZrO2,h-BN,2 dimension,X-ray
更新于2025-09-04 15:30:14