EXCITON DYNAMICS AND SPIN RELAXATION IN UNSTRAINED AND TENSILE-STRAINED QUANTUM-WELLS

We have investigated exciton dynamics and spin relaxation in a GaAs/Al As multiple quantum well and in tensile-strained GaAs1-xPx/Al0.35Ga0.6 5As quantum wells. The studies have been done by picosecond time-resol ved photoluminescence spectroscopy. The strain introduced by the prese nce of phosphorous in the GaAs1-xPx/Al0.35Ga0.65As quantum wells modif ies the subband dispersions, permitting access to new structures that include the possibility of the light-hole exciton's being the first ex cited state of the system. Our studies have focused on the influence o f the different subband dispersions on exciton dynamics and spin relax ation. We have found that the exciton formation and the spin relaxatio n times decrease for the quasi-degenerate heavy-hole-light-hole excito nic ground state and that the recombination time depends essentially o n the character of the excitonic ground state. (C) 1996 Optical Societ y of America.