Impact of PbS quantum dots on GaAs photoluminescence

Light emission from PbS quantum dots (QDs) is an intriguing topic from application perspectives, and even after myriad of articles, still has open questions. The paper highlights the optical characterization of PbS QDs deposited via solvent deposition on semi-insulating GaAs substrates. The QD thin films were characterized by two-photon excited photoluminescence (TPL) measurements, exciting the samples with increasing pulsed laser (1064 nm, 10 Hz, 26 ps) intensities. The work reveals alterations of the optical properties of GaAs when hetero-paired with PbS QDs, as demonstrated by the trend of the TPL peak increase, the energy where the TPL peak takes place, and the overall dynamics of the peak shift. We also report that the TPL intensity increase of PbS QDs shows the same trend as the single-photon excited emission, and observed photo-induced doping of the QDs, i.e., the dynamic Burstein-Moss blue shift. The work stresses the possibility to modify the optical properties of semiconductor hosts by means of heteropairing with QDs. Through this work, we further attempt to reconcile observations, which are much different from reported classical models in semiconductor heterostructures.