Figure 1 shows an example of IF-VF curve for each temperature of forward voltage of SiC (Silicon Carbide) SBD. In the region where the IF is small, the forward voltage (VF) decreases as the temperature rises as in the case of Si diodes (Fig-2), but when the current is high, the forward voltage rises with increasing temperature.
This change is caused by heat change of the resistance component of the semiconductor.
There are two factors: (1) diffusion of electrons by lattice vibration and (2) excitation to the conduction band of donor electrons.
Wide-band-gap semiconductors such as SiC have strong bonding force and the influence of lattice vibration becomes larger than in the case of Si. Moreover, because the band gap is large, the donor becomes harder to excite than Si. These facts are considered to indicate the characteristics shown in the figure. For Si diodes, the temperature coefficient is inverted at high current exceeding the rated current.
Therefore, when Si diodes are connected in parallel, there is a possibility of thermal runaway. In SiC SBD, parallel connection can be comparatively easily constructed.