Two-dimensional exciton dynamics and gain formation processes in InxGa1-xN multiple quantum wells

Abstract

We investigated exciton dynamics in InxGa1-xN multiple quantum wells at 2 K and room temperature by means of time-resolved photoluminescence and pump-and-probe measurements. Under low excitation density, the temporal change of the spontaneous emission indicated slow dynamical features of the two-dimensional exciton localization, while, above a stimulation threshold density, the decay time of the emission was shortened to be less than 30ps due to the stimulated emission process. Further, the time-resolved pump-and-probe measurement revealed a fast relaxation of photoexcited delocalized electron-hole (e-h) pairs into localized states. Above stimulation threshold, localized states were saturated, and e-h pairs at delocalized states were observed. Two-dimensional e-h pairs at delocalized states relaxed into localized states and excitons were formed, from which the optical gain was formed in terms of the stimulated emission process. © 1999 American Physical Society.