To clarify the current research situation and offer a better understanding of the reliability for silicon carbide (SiC) power metal-oxide-semiconductor field-effect transistors ( mosfet s), a comparison among the reliability mechanisms between planar-gate (PG) and trench-gate (TG) SiC power mosfet s, which have not been comprehensively summarized, is made in this article. The latest studies focusing on the reliability issues of commercial SiC mosfet products, including the PG device, the double-trench device and the asymmetric TG device, are reviewed. For the existing of the gate trenches and the unique structures protecting them, SiC TG mosfet s express quite different instability phenomena from the PG ones under various ultimate and long-term electro-thermal stresses. The influences of these stresses closely related to the practical operation conditions on SiC power mosfet s, including the avalanche stress, the short-circuitstress, the surge current stress of the body diode, and the switching stress, are discussed and reviewed in details.

The degradations of electrical parameters for silicon carbide power MOSFETs under repetitive short-circuit (SC) stress are investigated in detail in this paper. It demonstrates that the generation of negative charges along the gate-oxide interface of the channel region is the dominant degradation mechanism, which results in the increase in the threshold voltage (Vth) and the rise of on-state resistance (Rdson) under low gate voltage bias condition. Furthermore, degradations of dynamic characteristics including gate charge (Qg) and switching behaviors of the device after the repetitive SC stress are extracted and analyzed for the first time. It illustrates that the increased Vth contributes to the rise of the Miller plateau voltage (Vgp), which further leads to the increase in gate-source charge (Qgs). Meanwhile, the increase in the turn-on time and the reduction of turn-off time are observed, which are also resulted from the positive shifts of Vth and Vgp, leading to the rise of turn-on switching energy (Eon) and the decline of turn-off switching energy (Eoff), respectively.

Degradations of dynamic characteristics for SiC power MOSFETs under repetitive avalanche shocks are investigated in details. With the help of Silvaco TCAD simulations, Cg-Vg measurement and three-terminal CP test, the main damaged position is demonstrated to be the SiC/SiO2 interface along JFET region instead of the body diode where most avalanche current paths through. Dominant avalanche degradation mechanism is then confirmed to be the injection of holes into the gate oxide above JFET region. Since the channel region and the main junction of body diode are not seriously damaged by avalanche stress, static parameters all remain stable. Meanwhile, due to the injection of holes, the depletion layer beneath JFET region gets thinner, resulting in the increase of Cgd under low Vds bias condition. It further takes responsibilities for the increments in Ciss, Coss and Crss. Moreover, it results in the extension of Miller plateau. Therefore, increase of gate charge and delay of turn-off time after being stressed by repetitive avalanche shocks are monitored. Moreover, turn-on and turn-off dissipated energies after different UIS stress cycles are extracted. They are rarely influenced by the stress for the overlapping areas of voltage and current during switching procedures are relatively stable.

The degradations of electrical parameters for double-trench silicon carbide (SiC) power metal-oxidesemiconductor field-effect transistors (MOSFETs) under repetitive avalanche stress are investigated in this paper. The injection of hot holes into the bottom oxide of the gate trench during avalanche process is demonstrated to be the dominant degradation mechanism, while the channel is rarely influenced by the stress. The injected holes attract extra electrons in the SiC layer along the SiC/SiO ₂ interface, decreasing the ON-state drain-source resistance (R _dson ). Due to this reason, the threshold voltage (V _th ) of the device also reduces slightly. Moreover, other than static electrical parameters, dynamic characteristics including the gate-drain capacitance (C _gd ) and the switching characteristics of the device also degrade. After being stressed by repetitive avalanche stress, the depletion region beneath the bottom of the gate trench gets thinner, leading to the increase in C _gd , which further influences the switching behaviors. The turn-ON and turn-OFF switching times of the device are calculated. It illustrates that the repetitive avalanche stress results in an obvious delay in the turn-OFF procedure, but hardly influences the turn-ON behaviors of the double-trench SiC MOSFET.

This letter firstly reveals the single pulse unclamped-inductive-switching (UIS) withstanding physics and failure mechanism for p-GaN high electron mobility transistor (HEMT) with Schottky type gate contact. Unlike Si/SiC-based devices, the p-GaN HEMT withstands the surge current from load inductor by storing the energy into the output capacitance of the device, rather than dissipating the energy by avalanche process. To describe the UIS process, physics-based models are proposed. Also, by the simulations and de-cap/de-layer experiments, the failure mechanism is presented as a different manner compared with Si/SiC-based devices. The high voltage during the UIS process introduces high electric field near the drain contact, which leads to the inverse-piezoelectric effect, then bringing the rise-up of the leakage current and high power dissipation. As a result, the region near drain contact is burned by thermal runaway. Moreover, it is demonstrated that higher bus voltage and larger load inductance will increase the UIS-induced failure risk, while the gate resistance, turn-off gate voltage and ambient temperature exhibit little influences upon the UIS withstanding capability of the device.

Life detection radar can detect human physiological signals (respiration, heartbeat, body movement, etc.) from a long distance away by penetrating nonmetal mediums (brick walls, ruins, etc.). However, interference is often caused by respiratory movements of the radar's operator when detecting vital signs of another human target. The detection accuracy can be significantly influenced by this kind of interference. In this letter, an experimental setup with a dual-frequency continuous-wave life detection radar is investigated. The system operates with different frequencies of 5.75 and 35 GHz. An adaptive filtering method is applied to suppress the interference caused by the operator's respiratory movements. Experimental results show that this method can effectively suppress respiratory interference and improve detection accuracy.