# A Simulator for Investigation of Breakdown Characteristics of SiC MOSFETs
## 1 Introduction  
Silicon carbide (SiC) has emerged as an attractive candidate for high power-density switching applications due to its superior material properties. SiC has three times the bandgap width, ten times the critical electric field, three times the thermal conductivity and nearly twice the saturation velocity of silicon (Si). In addition, the three-times bandgap width of SiC results in an intrinsic carrier concentration 18 orders of magnitude lower than that of Si [1; 2; 3; 4]. These attributes demonstrate significant potential for developing power devices capable of operating at higher power levels, elevated temperatures and increased frequencies, while maintaining reduced leakage currents. Among the various polytypes, the 4H-SiC crystal structure stands out as a commercially accessible option due to its wider bandgap, higher carrier mobility compared to other polytypes, exhibiting superior electrical properties [5; 6].  
SiC-based power metal oxide-semiconductor field-effect transistors (MOSFETs) are favored for their low gate input impedance, fast switching speed and reduced on-resistance relative to other power devices [7; 8]. The high electric breakdown field of SiC enables these MOSFETs to switch power much faster than comparable silicon devices, resulting in lower energy losses. Consequently, breakdown voltage (BV) is considered a critical parameter for power devices [9; 10]. In order to accurately and comprehensively evaluate the breakdown voltage of 4H-SiC devices and further design and optimize device performance, accuracy and efficiency simulating the I-V characteristics and breakdown characteristics are essential.  
However, the wide bandgap of 4H-SiC results in an extremely low intrinsic carrier density of about 5 \(\times\) 10\({}^{-9}\) cm\({}^{-3}\) at room temperature [11], compared to 1 \(\times\) 10\({}^{10}\) cm\({}^{-3}\) for Si. This low intrinsic carrier concentration causes underflow, convergence issues and sharp carrier density variations. These make the simulation of 4H-SiC devices, especiallybreakdown voltage, challenging for numerical simulations. While using higher arithmetic precision and adaptive mesh dissection strategies [12] could improve the convergence problem, it is still worth exploiting to achieve better numerical stability. Moreover, to achieve more accurate device simulation, modifications to existing models or the development of new ones are often required. Independent and flexible device simulators are needed to incorporate these models. Therefore, this work demonstrates a robust simulator for 4H-SiC with high numerical accuracy and convergence, to provide an accurate analysis of the breakdown characteristics and device performance.  
The main aim of this paper is to employ a self-developed simulator to investigate the breakdown characteristics of 4H-SiC MOSFETs. The remaining contents of the paper are arranged in the following manner. Section 2 outlines the simulator's framework, explicates the numerical methods for scaling independent variables in fundamental equations to improve numerical stability, discusses the discrete methods used in the simulator, and presents the physical models included. For validation, comparisons are made with both experimental results and commercial TCAD. Section 3 discusses the breakdown characteristics' dependence on the lattice temperature, device geometry and doping profile. Finally, conclusions are drawn in Section 4.