Comparison of polysilicon and silicon-carbon emitters with enhanced emitter efficiency

Plasma-Enhanced CVD (PECVD) and Low-Pressure CVD (LPCVD) silicon-carbon emitters have been fabricated in the same transistor layout together with the best conventional implanted polysilicon emitters. In this way the first direct comparison of DC-transistor characteristics has been made. The highest emitter Gummel numbers are achieved for PECVD silicon-carbon emitters (up to 92*10/sup 12/ s/cm/sup 4/ compared to 66*10/sup 12/ s/cm/sup 4/ for the best implanted polysilicon emitter), whereas emitter series resistance is acceptably low (0.97*10/sup -6/ /spl Omega/*cm/sup 2/). Moreover, the thermal budget for emitter formation is extremely low (30 minutes at 750/spl deg/C).