Abnormal photoluminescence for GaAs/Al0.2Ga0.8As quantum dot-ring hybrid nanostructure grown by droplet epitaxy

The optical properties have been investigated for the GaAs/Al0.2Ga0.8As quantum dot-ring hybrid nanostructures grown by droplet epitaxy, in which each nanostructure consists of four quantum dots (QDs) sitting on a distinct ring of GaAs. A blueshift and narrowing of the photoluminescence (PL) spectra along with the nonlinear decay of the time-resolved PL curves of the QDs have been observed. These abnormal PL behaviors are caused by the unique state filling effect correlated with the quantum dot-ring structure feature, which is strongly affected by carrier transfer from smaller dots to larger dots via the wetting ring in the GaAs/Al0.2Ga0.8As hybrid structure.