A transistor model for numerical computation of forward-bias second-breakdown boundary

A two-dimensional bipolar transistor model for numerical computation of forward-bias, second-breakdown boundary which takes into account high-current density effects such as Kirk´s effect and avalanche injection is proposed. The model was verified experimentally on BU326 power transistors. The numerically determined forward-bias safe operating area is in good agreement with the experimentally determined one, especially at high collector currents and lower collector voltages. The model is also used to analyze the dynamics of the forward-bias second breakdown. It was found that, at high collector current and low collector voltages, second breakdown may also occur due to avalanche injection. The model is suitable for parametric study of forward-bias second breakdown.