Characterization of non-ohmic behavior of emitter contacts of bipolar transistors

Emitter contacts of bipolar transistors, with silicide or polysilicon contacts, are electrically characterized by analyzing the deviation of the base current at high currents from its ideal exponential behavior. A simple theory is presented that explains the deviation of the series voltage drop from ohmic behavior, observed in some of the devices with polysilicon emitter contact, in terms of an interface with tunneling properties.