The second breakdown in reverse biased transistor as an electrothermal switching

A thorough investigation has been given to second breakdown (SB) behaviors in transistors under reverse biased-base condition, and three types of behaviors have been shown: normal (without SB), and partial SB, as well as complete SB, which appear after very short delay times. The last two behaviors are shown to involve an electrothermal switching mechanism which operates at emitter collector voltages above the open base avalanche value V
ECO
(a* > 1). Effects of local base punchthrough are shown which may also be important in some forward bias SB behaviors.