Experimental proof of current bifurcation and mutual heating in bipolar transistor arrays

We present experimental proof of the electro-thermal bifurcation and mutual heating in bipolar transistor arrays using photon emission microscopy. With this technique, no electrical probing of each individual transistor in the array is needed but optical measurements allow accurate determination of the electro-thermal effects. For identically processed transistors in an array, we show that current bifurcation and mutual heating can be observed as sequentially optical switching of each transistor. Such optical and electrical switching effect can be explained and described using the individual transistor critical collector current theory after including mutual heating.