MgAl2O4 microwave dielectric ceramics were modified by Zn substitution for Mg, and their dielectric characteristics were evaluated, along with their structures. Dense (Mg1−xZnx)Al2O4 ceramics were obtained by sintering at 1550°–1650°C in air for 3 h, and the (Mg1−xZnx)Al2O4 solid solution was determined in the entire composition range. With Zn substitution for Mg, the dielectric constant ɛ of MgAl2O4 just varied from 7.90 to 8.56, while the Q×f value had significantly improved up to a maximal value of 106 000 GHz at x=1.0. Moreover, the τf of MgAl2O4 ceramics had declined from −73 to −63 ppm/°C.

Infrared reflection spectra of (Mg1−xZnx)Al2O4 ceramics were analyzed by Kramers–Kroning analysis and classical oscillator model simulation. The dielectric properties were extrapolated down to the microwave range using the classical oscillator model for fitting the dielectric function. According to structure analysis, the losses originating from bend vibration and stretch vibration of the bond between A‐site cation and oxygen anion dominated the whole dielectric losses of the spinel ceramics. The coexistence of Mg and Zn deteriorated the intrinsic dielectric properties due to the bond asymmetry thus introduced. The calculated Qf (∼105 GHz) was much higher than the measured ones (∼104 GHz), suggesting that the extrinsic loss was significant. Therefore, the microwave dielectric properties of MgAl2O4 and ZnAl2O4 could be improved much by microstructure modification, and the little superiority in their solution compared with the end‐members was due to microstructure improvement.

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Optimum n-drift region of a 4H-SiC Junction Barrier Schottky Diode (JBS) was analyzed by simulation with consideration of the anisotropic impact ionization. According to the detailed simulations using SRIM and Sentaurus, model parameters of empirical equations were obtained through fitting, which showed that the anisotropic avalanche model (2D-ANISO) differs significantly from the 1-dimensional empirical model (1D-Cooper) and the old isotropic avalanche model (2D-ISO). These initial results suggested that the JFET resistance and anisotropic impact ionization should be taken into account during the optimization of a 4H-SiC JBS in which field crowding at the corner of p-grid causes higher reverse leakage current.

The 10 kV silicon carbide p-channel insulated gate bipolar transistors (IGBTs) with low forward voltage drop (VF) have been fabricated and characterized successfully. The novel edge termination structure of Four-Region Multistep Field Limiting Rings (FRM-FLRs) and the optimum JFET region design proposed in our previous work is adopted to improve the blocking performance and the on-state characteristics. The fabricated device with a chip size of 6 mm × 6 mm and an active area of 0.16 cm2 exhibits a high blocking voltage of -10 kV with a small leakage current below -200 nA. Meanwhile, a low forward voltage drop of -8 V at the collector current of -10 A with a gate bias of -20 V is obtained at room temperature, corresponding to a current density of 62.5 A/cm2. Besides, a lower gate leakage current is measured less than 2 nA at the gate voltage of -30 V. Experimental results demonstrate that a better trade-off between the blocking voltage and the on-state characteristics is achieved for the fabricated device, which is desirable for the high power applications.