DYNAMICS OF CARRIER-CAPTURE PROCESSES IN GAXIN1-XAS/GAAS NEAR-SURFACE QUANTUM-WELLS

GaxIn1-xAsx/GaAs quantum wells with thin top barrier layers in the range of a few nanometers have been studied by time resolved photoluminescence spectroscopy. The excitonic lifetime is strongly influenced by a fast trapping mechanism of carriers into surface states. By varying the top barrier thickness the influence of the surface on the optical properties of quantum wells with different well thicknesses was investigated. We observe a simultaneous decrease of the photoluminescence intensity and lifetime below about 10 nm top barrier thickness. The onset of the decrease scales with the quantum well width and begins for thinner quantum wells at thicker top barrier layers. Calculations assuming electron capture times shorter than 1 ps into surface states located within a trapping layer of about 5 nm thickness reproduce the experimental results very well. © 1995 The American Physical Society.