High power bipolar transistors require the use of multiple emitters which, at high current densities, show significant self-heating and temperature increases. In this study we use a multiemitter SiGe HBT, with multiple emitter contacts, to examine the temperature distribution in the emitters in such a device. By biasing one emitter at a time and using the other base-emitter junctions as thermometers we have measured the temperature increase in different emitters and effectively the thermal coupling between the emitters. We compare the data with simulations for a simple thermal model. (C) 2004 American Vacuum Society.