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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]

Radiation effects of 3-MeV protons on 4H-SiC bipolar devices and integrated OR-NOR gates have been investigated. The chips were irradiated from a fluence of 1 \times 10^8~\cm^-2 until 1 \times 10^13~\cm^-2. Up until a fluence of 1 \times 10^11~\cm^-2, both the bipolar devices and the logic gates were found to be stable, but for higher fluence, they begin to degrade as a function of irradiation fluence. Using TCAD simulations, degradation of the transistor current gain has been found to be more dominated by surface states than bulk defects generated by the proton irradiation. Simulations of logic circuits using SPICE show that the gain degradation is the key contribution to the unstable performance of the circuits from the fluence of 1 \times 10^12~\cm^-2 and above. [ABSTRACT FROM PUBLISHER]