EXCITON DYNAMICS OF GAAS/ALXGA1-XAS DOPED QUANTUM-WELLS

The interaction of excitons with impurities in an intentionally doped GaAs/AlxGa1-xAs quantum well has been studied using picosecond time-resolved photoluminescence employing resonant excitation. The dominance of exciton recombination in a quantum structure allows a detailed analysis of the interaction kinetics, not previously possible in bulk GaAs. The recombination kinetics on a picosecond time scale are found to be strongly dependent upon the doping level, temperature, and well width. The contribution of these terms to the balance of the population between free excitons and impurity-bound excitons is investigated. A numerical solution of the associated differential equations allows a quantitative evaluation of the parameters describing this interaction (for a 100- acceptor-doped QW at 5 K we obtain the exciton lifetime FE180 ps, the bound exciton lifetime BE450 ps, and the capture rate for free excitons to neutral acceptors CFE cm2 s-1). A consistent picture of the capture and thermal emission processes for excitons at neutral acceptors and their effect on the observed quantum-well recombination transient emerges from this analysis. © 1994 The American Physical Society.