Effects of reverse-bias emitter-base stress on the cryogenic operation of advanced UHV/CVD Si- and SiGe-base bipolar transistors

This paper demonstrates for the first time that hot carrier injection resulting from reverse-bias emitter-base (EB) stress at 300 K can result in significant shifts in the low-temperature electrical characteristics of epitaxially grown Si- and SiGe-base bipolar transistors. At low injection, the observed temperature dependence of the stress-induced base current leakage is attributed to a Poole-Frenkel field-enhanced tunneling mechanism. We have also observed for the first time a minor enhancement of the low temperature collector current after EB stress at 300 K. This enhancement in the collector current is attributed to a slight modification in the emitter-to-base space-charge-region via stress-induced trapped-charge located at or near the spacer oxide separating the emitter-base contact regions.