The formation of single Shockley stacking faults (SSSFs) in 4H-SiC crystals under non-equilibrium conditions (e.g., the forward biasing of PiN diodes and ultraviolet light illumination) is a key phenomenon in the so-called bipolar degradation of SiC power devices. This study theoretically investigated the physical mechanism of this phenomenon based on the concept of quantum well action. As a first approximation describing the non-equilibrium state of the material, we employed quasi-Fermi level approximation. We then made improvements by considering several physical effects governing the carrier distribution near and in the SSSF. The improved model accounts well for the excitation threshold and the temperature dependence of SSSF expansion. Thus, the model provides useful insights into the driving force of SSSF expansion under non-equilibrium conditions.

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The annealing behavior of electrical resistivities perpendicular and parallel to the basal plane of heavily nitrogen-doped 4H-SiC crystals was investigated. The temperature dependencies of the resistivities exhibited characteristic behaviors after multiple rounds of high-temperature annealing (1100°C, 30 min). High-temperature annealing induced stacking fault formation to various extents in heavily nitrogen-doped 4H-SiC crystals. Based on these results, we discuss the cause and mechanism of the observed annealing-induced changes in electrical resistivities of the crystals.