Critical importance of the single-level approximation to account for the highly nonmonotonic dependences of carrier lifetimes on recombination impurity concentration

This paper is a continuation of an analysis regarding an increase in the lifetimes of nonequilibrium electrons π_n and holes πp by several orders of magnitude, observed with increasing concentration of recombination centers. It is shown that a substantial increase in πn and πp may also occur for three charge states of the recombination impurities N, and the curves πn=f(N) and π n=f(N) may each have two minima and maxima. Pis’ma Zh. Tekh. Fiz. 23, 39–45 (April 12, 1997)