Simulation and experimental study of 3-step junction termination extension for high-voltage 4H-SiC gate turn-off thyristors

•We design and simulate the 4H-SiC NPN structure with a 3-step JTE.•The distribution of the electrical field in the JTE region has been analyzed.•The experimental results are in good agreement with the simulated results.•The fabricated NPN structure with a 3-step JTE reaches a breakdown voltage of 7630 V. The 4H-SiC NPN structure with a 3-step junction termination extension (JTE), which shows a great capability for control of both the peak surface and bulk electric fields at breakdown, has been investigated and optimized using Synopsys Sentaurus, a two-dimensional (2-D) device simulator. The experimental results show that the NPN structure with an optimized 3-step JTE can accomplish a high breakdown voltage of 7630V, reaching more than 90% of the ideal parallel plane junction breakdown voltage. A good agreement between simulation and experimental results can be observed. The key step in achieving a high breakdown voltage is controlled etching of the epitaxially grown n-doped layer to reach the optimum depth and balanced charge in the multistep junction termination extension (MJTE) layer.