A novel 4H-SiC Multiple Stepped SGT MOSFET (MSGT-MOSFET) is presented and investigated utilizing TCAD simulations in this paper. We have quantitatively studied the characteristics of the device through simulation modeling and physical model calculations, and comparatively analyzed the performance and application prospects of this novel device. The gate-to-drain capacitance (C_gd) and gate-to-drain charge (Q_gd) of the MSGT-MOSFET are significantly reduced in comparison with the double trench MOSFET (DT-MOSFET) and the conventional SGT MOSFET (CSGT-MOSFET), due to the reduction of the overlapping area of the split gate (SG) structure and drift region. Therefore, the obtained high frequency figure of merit (HF-FOM) defined as [R_on × C_gd] reduced by 23.9% compared with DT-MOSFET and CSGT-MOSFET. And the HF-FOM [R_on × Q_gd] for the MSGT-MOSFET significantly decreased by 71% and 50%, respectively, compared to that of the DT-MOSFET and CSGT-MOSFET. Furthermore, the switching loss is also simulated and calculated. And the total switching loss of the proposed MSGT-MOSFET realizes 42.9% and 21.7% reduction in comparison with the DT-MOSFET and CSGT-MOSFET. The overall enhanced performances suggest that the MSGT-MOSFET is an excellent choice for high frequency power electronic applications.

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To investigate the unclamped inductive switch (UIS) characteristics, 1200 V silicon carbide (SiC) planar MOSFETs with four cell topologies of linear, current sharing linear, square, and hexagon are designed and manufactured. The experimental platform was built and tested. The results show that the single pulse avalanche energy density of the linear cell topology is 1.69 times higher than that of the square and 1.49 times that of the hexagon. Further, the UIS process is simulated by using physical simulation, which shows that the avalanche energy was concentrated near the corner of the P-base region in the UIS mode. From this, the avalanche energy distribution differences of the four cell topologies were analyzed and compared. A theoretical model of avalanche heating per unit area is proposed, which shows that the avalanche energy density is inversely proportional to the proportion of avalanche energy concentration region. This study may contribute to the cell topology design of SiC MOSFETs under the application scenario with high avalanche reliability requirements.@en

Sensitive materials for formaldehyde (HCHO) sensor need high sensitivity and selectivity. The research on two dimensional (2D) sensitive material is growing, and most studies focus on the pristine or modified graphene. So it is essential to introduce other 2D materials into HCHO gas sensor. In this report, the adsorption behaviors of organic gas molecules including C₂H₆, C₂H₄, C₂H₂, C₆H₆, C₂H₅OH and HCHO over indium triphosphide (InP₃) monolayer were studied by using first-principle atomistic simulations. The calculation results demonstrate that InP₃ monolayer has a high sensitivity and selectivity to HCHO than others. By comparing the structures and adsorption results of InP₃ monolayer, graphene and single-layered MoS₂, it was found that the polarity bonds and steric effect of the site on monolayer play an important role in the detection of HCHO. The effect of strain on the gas/substrate adsorption systems was also studied, implying that the stained InP₃ monolayer could enhance the sensitivity and selectivity to HCHO. This study provides useful insights into the gas-surface interaction that may assist future experimental development of 2D material for HCHO sensing and performance optimization based on strain.

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Predictive calculations based on density functional theory (DFT) are used here to study the electronic and optical properties of GeSe monolayer after adsorbing gas molecules (O₂, NH₃, SO₂, H₂, CO₂, H₂S, NO₂, CH₄, H₂O, NO, CO). Our results reveal that for all the gas molecules considered, only NH₃ is adsorbed on GeSe monolayer by physisorption. Whereas SO₂ and NO₂ are chemisorbed on GeSe monolayer with strong adsorption energies. In addition, the adsorption of O₂, NO and NO₂ distinctly enhances the optical absorbance and broaden the absorbance range of GeSe monolayer in visible light region. Also, it is found that the adsorption of H₂S, NO and NH₃ can reduce the work function of the GeSe monolayer. The results indicate that GeSe monolayer is not only a promising candidate for the sensing, capture, and storage of NH₃, but also an anticipated disposable gas sensor or metal-free catalyst for detecting and catalyzing SO₂ and NO₂. Furthermore, it has excellent potential to be applied to optical sensors, solar cells, nanoelectronics or optoelectronics devices.

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