Hierarchically constrained carrier dynamics in red-LED illuminated type-II InAs/GaSb superlattices

Abstract

We report on positive and negative persistent photo-effects observed in some red light emitting diode (LED)-illuminated type-II InAs/GaSb superlattices (SLs) grown on a p-type GaSb. By analyzing the time dependence of the transverse resistance during and after the illumination, we show that the rise and decay curves are logarithmic, a behavior which points to hierarchically constrained carrier dynamics. Accordingly, negative persistent effects are explained by diffusion and trapping of photo-excited carriers in the p-type buffer layer and their subsequent tunneling back to the SL. On the other hand, positive persistent effects are explained by a low density of majority-carrier trapping centers in the buffer layer. Hence, persistent photo-effects upon red-LED irradiation provide a diagnostic of the quality of the superlattice-buffer interface.