A model for stable hot spots in transistors

A model is proposed which accounts for the ability of a transistor hot spot to stabilize. It is shown that emitter current-crowding and base-widening play an important role in determining hot spot stability. Experimental results are given which show that the observed peak temperature is in good agreement with theoretical predictions. In addition, the measured onset of second breakdown is consistent with the hypothesis that a critical current density is reached which triggers a low voltage mode of operation. Finally, various precautions are described for interpreting forward second breakdown test data.