Coupling Induced Enhancement of Interface Recombination in GaAs Multiple Quantum Well Structures

The variation of luminescence transients of GaAs multiple quantum wells as a function of barrier widths is studied in the range between 0.87nm (superlattice) and 18.1 nm (uncoupled wells) by means of cathodo- and photoluminescence. With decreasing barrier width the nonradiative recombination rate is found to be drastically enhanced whereas the radiative recombination probability decreases. Thus a pronounced decrease of the quantum efficiency results. The controlled variation of the barrier width is found to be decisive for an unambigous identification of the origin of the traps: Comparison with a theoretical calculation shows that they are localized at the heterointerfaces and not in the barriers.