With the increase in voltage level and current capacity of the insulated gate bipolar transistor (IGBT), the avalanche effect has become an important factor limiting the safe operating area (SOA) of the device. The hole injection into the p/n junction on the backside of the IGBT after avalanche is the main feature that distinguishes the avalanche effect from other devices. In this paper, the avalanche breakdown characteristics of IGBT and the nature of current filament are investigated using theoretical analysis and numerical simulation, and the underlying physical mechanism controlling the nature of current filaments is revealed. The results show that the hole injection on the backside of the IGBT leads to an additional negative differential resistance (NDR) branch on the avalanche breakdown curve. The device’s common-base current gain, αpnp, is a crucial factor in determining the current filament. As αpnp increases, the avalanche-induced current filament becomes stronger and slower, resulting in weaker avalanche robustness of the device.@en

Inspired by the activation mechanism of slow anion channels 1 (SLAC1) in plants that proton pump reversibly induces plant stomata open for CO2 adsorption, a CO2-switching H+ conduction/HCO3− diffusion dual ion channel (CO2-switching-DIC) was constructed by assembling γ-cyclodextrin-MOF (γ-CD-MOF) and 3,4,9,10-perylenetetracarboxylic acid (PTCA) for CO2 chemiresistive sensing. The obtained CO2 sensor exhibited high response (Rg/R0 = 1.33, 50 ppm) and selectivity, low practical limit of detection (1 ppm) and excellent consistency (94.5%) with a commercial infrared CO2 meter at room temperature. It is indicated that hydrogen bond networks in CO2-switching-DIC will be enlarged with the increasing of carboxylic group’s content on perylene skeleton, thereby modulating proton conductivity at molecular level and furthermore CO2 sensing performance of the composite. The CO2-switching-DIC-based sensor has been utilized to distinguish the exhaled CO2 concentration between lung cancer patients and healthy individuals, illustrating its promising application prospect in non-invasive diagnose.@en

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