**4. Conclusions**

The authors' measurements show that the ambient temperature rises strongly a ffect certain characteristics and parameters of the silicon carbide power bipolar transistor. Moreover, the self-heating phenomenon in SiC BJT can result in not only qualitative but also quantitative changing of the semiconductor device characteristics shape, resulting in the negative slope of collector current with increasing collector-emitter voltage occurrence and causes decreasing of the current gain factor β with power dissipation increase.

In the typical Gummel–Poon model implemented in SPICE, the self-heating phenomenon is not taken into account. In this paper, the authors proposed an improved SiC BJT model dedicated for SPICE, incorporating not only the self-heating phenomenon, but also modeling the quasi–saturation mode using the temperature-dependent intrinsic carrier concentration model. Apart from this, the current gain factor model is used for the first time for the bipolar transistor made of silicon carbide taking the temperature and collector current impact into account. The proposed electrothermal model of the BT1206-AC SiC BJT allows calculating the non-isothermal characteristics of the tested device. The simulated and measured characteristics of considered SiC power BJT were compared. The satisfactory agreemen<sup>t</sup> between both the calculated and measured characteristics indicates the correctness of the presented model. It is worth mentioning that the accuracy of the proposed model can be achieved even at high current density when the current gain factor β starts to decrease.

**Author Contributions:** Investigation, J.P., D.B. and J.Z.; methodology, J.P., D.B. and J.Z.; supervision, J.Z.; writing—original draft, J.P., D.B. and J.Z.; writing—review and editing, J.P., D.B. and J.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Conflicts of Interest:** The authors declare no conflicts of interest.
