NONRADIATIVE RECOMBINATION VIA STRONGLY LOCALIZED DEFECTS IN QUANTUM-WELLS

Using time-resolved photoluminescence, we have studied the nonradiative recombination of excess charge carriers in oxygen-implanted GaAs/Al0.4Ga0.6As single quantum wells. In order to reveal the recombination mechanism, the carrier lifetime is measured as a function of temperature and well width. We observe a decrease of the measured lifetime with increasing implantation dose and the nonradiative part of the recombination rate increases with increasing temperature. We find that the nonradiative recombination is thermally activated and the activation energies increase with decreasing well width. Under the assumption of strongly localized deep impurities we can explain this behavior with multiphonon capture processes and an analysis of the well-width dependence of the activation energies allows for the determination of the coupling strength for electron capture. In agreement with deep-level transient-spectroscopy (DLTS) measurements we determine a deep level 430 meV below the conduction band.