Optimization of the selenium field-stop profile with respect to softness and robustness

Tailoring the field-stop layer is an effective measure to increase the switching softness and to improve the avalanche robustness of high-voltage power diodes. Diodes and IGBTs with deeper field-stop layers having a superior switching behavior can be created with a relatively low temperature budget by using selenium as field-stop dopant. In this work, we show that a further improvement of the diode performance can be achieved by using a selenium double-field-stop layer. Providing a CIBH-diode with such a selenium double field-stop layer results in a very soft and robust diode. The characteristic of the selenium traps (donor levels and capture cross sections) are determined by DLTS and by frequency resolved admittance spectroscopy measurements. Simulations of the reverse recovery behavior using these trap properties show good agreement with experimental results and are essential for finding further optimized field stop profiles.