2 research outputs found
Impact ionization fronts in Si diodes: Numerical evidence of superfast propagation due to nonlocalized preionization
We present numerical evidence of a novel propagation mode for superfast
impact ionization fronts in high-voltage Si -- structures. In
nonlinear dynamics terms, this mode corresponds to a pulled front propagating
into an unstable state in the regime of nonlocalized initial conditions. Before
the front starts to travel, field-ehanced emission of electrons from deep-level
impurities preionizes initially depleted base creating spatially nonuniform
free carriers profile. Impact ionization takes place in the whole high-field
region. We find two ionizing fronts that propagate in opposite directions with
velocities up to 10 times higher than the saturated drift velocity.Comment: 3 pages, 4 figure
Theory of superfast fronts of impact ionization in semiconductor structures
We present an analytical theory for impact ionization fronts in reversely
biased p^{+}-n-n^{+} structures. The front propagates into a depleted n base
with a velocity that exceeds the saturated drift velocity. The front passage
generates a dense electron-hole plasma and in this way switches the structure
from low to high conductivity. For a planar front we determine the
concentration of the generated plasma, the maximum electric field, the front
width and the voltage over the n base as functions of front velocity and doping
of the n base. Theory takes into account that drift velocities and impact
ionization coefficients differ between electrons and holes, and it makes
quantitative predictions for any semiconductor material possible.Comment: 18 pagers, 10 figure