Spatial and temporal modulation of exciton photoluminescence properties in GaAs/AlAs dynamic quantum dots formed by surface acoustic waves

We report on the dynamic optical properties of excitons in moving dots (dynamic quantum dots, DQDs) formed by the interference of orthogonally propagating surface acoustic waves (SAWs) in GaAs/AlAs quantum wells. Spatially and time-resolved photoluminescence (PL) measurements using a synchronized excitation method clearly demonstrate the formation of two interpenetrating square arrays of DQDs, one consisting of potential dynamic dots (p-DDs) formed by the SAW piezoelectric potential and the other consisting of strain dynamic dots created by the strain-induced band-gap modulation. We found that the p-DDs induce a PL-polarization anisotropy, leading to a checkered spatial modulation pattern for the preferential PL-polarization direction. Carrier dynamics under SAW fields, which affect the effective diffusion length of excitons and the PL quenching time, is invoked to clarify the physical mechanisms underlying the PL-mapping spectra obtained by the synchronized excitation method. A theoretical analysis on the band structures and optical transition properties modified by SAWs consistently explains the experimental results.