Influence of Concurrent Electrothermal and Avalanche Effects on the Safe Operating Area of Multifinger Bipolar Transistors

The impact of the concurrent action of electrothermal and avalanche effects on the reduction of the safe operating area is experimentally investigated for a wide number of single-, two-, and three-finger bipolar transistors fabricated in SiGe, GaAs, and silicon-on-glass technologies. The results of the analysis are substantiated by a SPICE-like simulation tool that allows the monitoring of the temperatures of the individual fingers and provides an in-depth understanding of the individual influence of the positive feedback mechanisms. Design strategies for minimizing the effects on device operation, like the implementation of ballasting resistors and emitter segmentation, are also analyzed.