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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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3.5: Investigation of excited-state dynamics upon both photo- and electro-excitation of thermally activated delayed fluorescent molecules
摘要： Exciton dynamics is one of the core issues lies in the field of achieving high efficiency organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) molecules. The authors briefly review the host dependence of TADF dopant, and then discuess the host–guest interaction in TADF OLEDs. By the means of transient electroluminescence measurement, the dynamics of triplet and singlet excitons are studied. Results show that host material with high T1 energy levels, large spectral overlap with TADF dopant’s absorption and free of exciplex formation exhibits higher TADF character. Furthermore, the underlying reason for the efficiency roll-off of the TADF OLEDs is clarified to be attributed to deeply trapped charges.
关键词： transient,trapped charges,excited-state dynamics,electroluminescence measurement
更新于2025-09-10 09:29:36