Evidence of lateral coupling in long wavelength vertically stacked InAs/GaAs(001) quantum dots

Abstract

1.3 m room temperature emitting multiple-stacked InAs/GaAs(001) quantum dots (QDs) are grown by molecular beam epitaxy (MBE) and investigated by photoluminescence (PL), polarized photoluminescence (PPL), photoluminescence excitation (PLE), time resolved photoluminescence (TRPL) and atomic force microscopy AFM. The PL measurement shows that two distinct sets of QDs coexist in the sample. The AFM image of the tenth QDs layer not only confirms the bimodal size distribution of the QDs but also shows that the large QDs are elongated along the [1-10] direction. The former structural information has been verified by PPL. Through the excitation density dependent PL and the detection energy dependent PLE we have evidenced two kinds of QDs within the small size dots population: isolated QDs and laterally coupled QDs with vertically coupled large size QDs. The large size dot population is found to possess a long PL decay time confirming that they are electronically coupled. In the meanwhile the PL decay time of the small QDs is found to be similar to that of single layer QDs. These results would help improve understanding some fundamental properties of an interesting structure for optoelectronic applications.