Seminar: Self-Organization in Complex Nonlinear Systems

Location: EW 731 (PN 731)

Time: Friday, 22.08.2008, 14:15

Impact ionization fronts in semiconductors: superfast propagation due to nonlocalized pre-ionization

Dr. Pavel Rodin (Ioffe Physico-Technical Institute St. Petersburg)

We consider impact ionization fronts propagating into semiconductor

with a constant electric field E_m in presence of small concentration

of free nonequilibrium carriers - so-called preionization. We show

analytically that if this concentration decays in the direction of

the front propagation with a small characteristic exponent λ, the

front velocity is determined by v_f = β_m/λ, where

β_m=β(E_m) is the corresponding ionization frequency. The

propagation velocity v_f can exceed the saturated drift velocity v_s

by several orders of magnitude even in moderate electric fields. We

discuss the physical reasons for the appearance of slowly decaying

preionization profiles in semiconductor devices and illustrate our

analytical findings with numerical simulations.

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