Evidence for excess carrier storage in electron-hole plasma in silicon transistors

This work presents experimental evidence for significantly greater charge storage in highly excited silicon near room temperature than conventional theory would predict. The experiments used low-doped collector regions of silicon bipolar transistors subjected to strong electrical excitations yielding an electron-hole (e-h) plasma having electron-hole pair densities up to about 4 × 10¹⁸cm^-3. As a possible interpretation, we connect these findings to a significant bandgap narrowing Δ EG(≃80 meV at 4 × 10¹⁸cm^-3). These data are compared with various data for Δ EG, in heavily doped silicon. Important device implications are discussed for integrated-circuit and discrete bipolar transistors and for photoconductivity switches.