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In this article, the static, dynamic, and short-circuit properties of 1.2-kV commercial 4H-SiC planar and trench gate metal–oxide–semiconductor field-effect transistors (MOSFETs) are compared and analyzed in a wide temperature range from 90 to 493 K. The temperature-dependent specific ON-resistance (${R}_{\text {sp}- \mathrm{\scriptscriptstyle ON}}$) and threshold voltage (${V}_{\text {th}}$) are analyzed in relation to the density of the interface state. The turn-on rise and turn-off fall times (${T}_{r}$ and ${T}_{f}$) and the corresponding energy loss (${E}_{r}$ and ${E}_{f}$) are extracted from a double-pulse test from cryogenic to high temperature and analyzed. The short-circuit capability of the two structures is studied at low temperature for the first time. The comprehensive comparison and analysis of the planar and trench gate MOSFET versus temperature in this work show the importance to study applications with SiC MOSFETs in a wide temperature range, especially for the cryogenic temperatures. [ABSTRACT FROM AUTHOR]

In this paper, an improved 4H-SiC U-shaped trench-gate metal–oxide–semiconductor field-effect transistors (UMOSFETs) structure with low ON-resistance (${R}_{ \mathrm{\scriptscriptstyle ON}}$) and switching energy loss is proposed. The novel structure features an added n-type region, which reduces ON-resistance of the device significantly while maintaining the breakdown voltage (${V}_{\textsf {BR}}$). In addition, the gate of the improved structure is designed as a p-n junction to reduce the switching energy loss. Simulations by Sentaurus TCAD are carried out to reveal the working mechanism of this improved structure. For the static performance, the ON-resistance and the figure of merit (FOM $= {V}_{\textsf {BR}}^{\textsf {2}}/{R}_{ \mathrm{\scriptscriptstyle ON}}$) of the optimized structure are improved by 40% and 44%, respectively, as compared to a conventional trench MOSFET without the added n-type region and modified gate. For the dynamic performance, the turn-on time (${T}_{ \mathrm{\scriptscriptstyle ON}}$) and turn-off time (${T}_{ \mathrm{\scriptscriptstyle OFF}}$) of the proposed structure are both shorter than that of the conventional structure, bringing a 43% and 30% reduction in turn-on energy loss and total switching energy loss (${E}_{\mathbf {SW}}$). [ABSTRACT FROM AUTHOR]

The influence of bulk traps in different regions of 4H-SiC bipolar junction transistors (BJTs) is investigated. The investigation is based on experimental results obtained by implanting up to \10^11\cm^-2 fluences of helium ions in the collector region. The results indicate that implantations, creating point defect concentrations in the range of the doping level, produce a sufficiently high concentration of traps to reduce the carrier concentration in this specific region. These traps degrade the device characteristics and are irrecoverable up to 500 ^\circ\C annealing. The experimental results are qualitatively analyzed by device simulations using a 2D numerical computer-aided design tool (TCAD). Systematic simulations are then performed by introducing traps at different locations in the BJT (i.e., emitter, base, and collector regions). The results indicate that the device performance is highly dependent on the defect concentration in the base region. The defects at different levels inside the collector also influence the device by producing a compensated layer in the material. However, the same concentration of defects (i.e., \sim\10^15\ \cm^-3) has less influence in the emitter region. [ABSTRACT FROM AUTHOR]

Degradation of \SiO2 surface passivation for 4H-SiC power bipolar junction transistors (BJTs) as a result of ion irradiation has been studied to assess the radiation hardness of these devices. Fully functional BJTs with 2700 V breakdown voltage are implanted with 600 keV helium ions at fluences ranging from \1 \times \10^12 to \1 \times \10^16\ \cm^-2 at room temperature. These ions are estimated to reach the \SiO2/ \SiC interface. The current–voltage characteristics before and after irradiation show that the current gain of the devices starts degrading after a helium fluence of \1\times \10^14\ \cm^-2 and decreases up to 20% for the highest fluence of ions. Simulations show that the helium ions induce ionization inside the \SiO2, which increases the interface charge and leads to a degradation of the BJT performance. Thermal annealing of the irradiated devices at 300 ^\circ \C, 420 ^\circ\C, and 500 ^\circ\C further increases the amount of charge at the interface, resulting in increased base current in the low-voltage range. [ABSTRACT FROM AUTHOR]