Lateral variation of interface disorder in wetting layer on formation of InAs/InP quantum dots visualized by near-field imaging spectroscopy

Near-field photoluminescence imaging spectroscopy of a wetting layer of InAs/InP quantum dots (QDs) at the critical thickness of 2.4 monolayers (ML) is used to visualize the spatial variation of the interface disorder. The wetting layer has a significantly lower density of carrier localization centers than a 2-ML thick InAs/InP quantum well, particularly in the vicinity of the QDs. This indicates that atomic-scale interface disorder is reduced during the initial stages of QD formation; in contrast, disorder remained far from the QDs.