**1. Introduction**

While the power MOSFET made of silicon carbide (SiC) is currently the most popular switching power wide bandgap-based semiconductor device, the SiC bipolar junction transistor (BJT) is still an inviting counterpart dedicated to high-temperature/high-power systems, due to its particular properties, such as low specific on-resistance, a less complicated manufacture method and its being free of oxide reliability referred to the high value of the electrical field and temperature. Since the last decade, the market has been o ffering high voltage silicon carbide power BJTs [1–5].

The research subject in this paper is the high voltage BJT made of silicon carbide, BT1206-AC manufactured by the TranSiC company and placed in a typical TO-247 case. The values of the certain parameters of this transistor are demonstrated in Table 1 [5].


**Table 1.** Parameter values of the BT1206-AC transistor.

Due to the improved electrical and thermal properties of silicon carbide devices compared to silicon devices, companies state that designers will want to replace silicon components for applications such as hybrid electric vehicles, inverters of solar cells and high power electric motor controllers with their silicon carbide counterparts. For all these applications, silicon carbide can solve the problems with a high-temperature environment and switching losses.

The ambient temperature has a strong impact on certain characteristics and parameters of the silicon carbide power bipolar transistors [4,6–8]. Moreover, in real operating conditions, due to the self-heating phenomenon, the junction temperature exceeds the ambient temperature because of the device dissipated thermal power converted into the heat in non-ideal heat dissipation conditions. The self-heating phenomenon, resulting in qualitative and quantitative changes of the semiconductor device characteristics shape, is observed as well in SiC BJTs [6].

In order to properly analyze the operation of SiC BJT-based electronic systems, a precise and relatively simple SiC BJT model for circuit simulation and trend analysis is needed. One of the earliest semi-physical models for silicon BJT is the Gummel and Poon model (G–P model) proposed in 1970 [9]. The G–P model has become a fundamental model for characteristics calculation of BJT in SPICE (Simulation Program with Integrated Circuit Emphasis) which is a popular computer tool that allows the analysis of characteristics and parameters of electronic components and systems [7,10–14]. Certain modifications have been made to evolve SiC BJT models in recent years. In 2004, the G–P model was applied to calculate the characteristics of SiC BJT for the first time [15]. Johannesson and Nawaz established a G–P-based analytical SPICE model for SiC BJT power modules that is useful for the designing of power electronics systems containing considered devices [16]. However, these models do not take into account the self-heating phenomenon. There are some electrothermal models (ETMs) dedicated to SiC BJT transistors in the literature [6,17,18], but works describing these models do not contain full information enabling their implementation in the SPICE program (e.g., no description of the controlled sources used in the model) or use numerical models that are complex, demand specific data concerning material features or device geometry and have time-consuming simulations.

This paper refers to the issue of modelling of static characteristics of SiC power BJTs including the self-heating phenomenon. The electrothermal model of SiC BJT has been proposed. The model was experimentally examined by comparison of the measured and simulated isothermal and non-isothermal characteristics of the selected transistor. The e ffect of self-heating on transistor characteristics was assessed and discussed. In this paper, the experimental verification of the model has been performed using a single device characterization, however, future work will include verification results based on a larger population of the considered class of devices.
