Temperature dependence of minority electron mobility and bandgap narrowing in p/sup +/ Si

Measurements of the temperature dependence of minority electron mobility mu /sub n/ and band gap narrowing Delta E/sub G/ for moderate to heavily doped p-type Si are reported. Bipolar transistor test structures to measure these have been fabricated on uniformly doped bulk and epi Si:B. Preliminary results indicate that mu /sub n/ increases strongly with decreasing temperature for the most heavily doped layers. Delta E/sub G/ for these samples decreases with temperature. In the moderately doped samples mu /sub n/ and Delta E/sub G/ are roughly constant. The results suggest that higher performance npn bipolars than were previously thought possible can be made for cryogenic operation with high-mobility p+ base regions; the reduced band-gap narrowing, however, suggests that a low-concentration emitter is essential.<>