The perforated emitter contact effect

A new phenomenon, the perforated emitter contact effect, is described. It arises when numerous extremely small gaps or perforations are introduced to an interfacial oxide layer in the emitter region of a bipolar transistor. Two-dimensional simulation of a novel emitter structure that incorporates a perforated interfacial layer indicates that such a layer can provide significant current gain enhancement with a negligible increase in series emitter resistance. These results have implications for polysilicon emitter bipolar transistors and suggest that significant tradeoffs between emitter resistance and current gain can conceivably be obtained if an intentionally grown interfacial oxide layer is thermally annealed so as to break up the oxide just enough to create numerous small perforations.<>