Clear observation of sub-band gap impact ionization at room temperature and below in 0.1 mu m Si MOSFETs

We report the first clear observation of the onset of impact ionization at 0.6V and 0.8V in O.1 mu m Si devices operating at 170K and 300K, respectively. These onset voltages were directly extracted from experimental bell-shaped substrate currents constituting clear evidence of impact ionization below the band gap of silicon. At low temperatures we observe simultaneous reductions in the threshold voltage for impact ionization, and the impact ionization current. These results suggest the operation of possible new mechanisms in addition to the usual carrier/carrier and carrier/optical phonon interactions.<>