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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]

A high gamma radiation hardness of 4H-SiC circuits is performed. The OR NOR circuits are based on emitter coupled logic (ECL), using integrated bipolar NPN transistors. Gain degradation in individual bipolar junction transistors (BJT) is minimal up to a dose of 38 Mrad (SiO2), but for the dose of 332 Mrad (SiO2) a degradation of 52% is observed. The SiC BJTs show higher radiation hardness than existing Si-technology and high stability under temperature stress. It is proposed that the oxide charge-dominated recombination is the key base current recombination mechanism contributing to gain degradation. An improvement in the gain is seen after annealing at 400 °C for 1800 s due to the possible annealing of some of the oxide defects contributing to the oxide charge. [ABSTRACT FROM PUBLISHER]

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]