Bipolar device scaling limits from tunneling in base-emitter junctions

Substantial tunneling currents in emitter-base junctions at lower doping levels than previously expected (1) have been observed, and are shown to be the result of high electric fields in shallow, scaled n⁺-p junctions. The distinctive form of the reverse I-V curves is theoretically explained and verified by measurements on shallow n⁺-p diodes. The appearance of a tunneling current is ascertained by the temperature dependence, which also allows a clear distinction of other current mechanisms. It is shown how C-V data can be analyzed to obtain an experimental value for the maximum electric field in the junction, which is essential in predicting the I-V characteristics of scaled bipolar transistors.