Minority carrier injection in relaxation semiconductors

Abstract

On the basis of normalized continuity equations solved by numerical procedures, it is shown that the predicted Van Roosbroeck depletion of majority carriers does indeed occur, not only in materials of near-zero lifetime ${\tau }_0$ but whenever $\frac{{\tau }_0}{{\tau }_D}<1\mathrm{}$, where ${\tau }_D$ is the dielectric relaxation time. A recombination front appears for $\frac{{\tau }_0}{{\tau }_D}\ll 1$ and/or high currents. Carrier concentrations, field, and recombination rate are evaluated as a function of distance from the injecting boundary, and the implications for the voltage-current characteristic are analyzed. In contrast to the lifetime case, the computed characteristics show an extended linear region, resulting from the opposed tendencies of of majority-carrier depletion (sublinear) and minority-carrier injection (superlinear). Total resistances higher than those calculated on the basis of the unperturbed bulk resistivity have not been found for the conditions investigated.