Hetero-emitter-like characteristics of phosphorus doped polysilicon emitter transistors. Part I: band structure in the polysilicon emitter obtained from electrical measurements

This paper reports on the cause of hetero-emitter-like characteristics recently discovered for a phosphorus doped poly-Si emitter transistor, the poly-Si emitter of which is crystallized from an in-situ phosphorus doped amorphous Si film. The band structure in the poly-Si emitter is investigated using (1) the transistor characteristics and (2) the I-V characteristics of the interface between the poly-Si emitter layer and the Si substrate. As a result, a new kind of potential barriers are observed on the conduction band and the valence band at the interface. The potential barrier on the valence band is proved to be the origin of the hetero-emitter-like characteristics. According to the I-V characteristics of the interface, the formation of the barriers is probably due to band discontinuity at the interface