Lateral carrier transfer for high density InGaAs/GaAs surface quantum dots

Abstract In(Ga)As surface quantum dots (SQDs) are promising candidates for surface-sensitive detection applications. As such, studies of the carrier dynamics are indispensable when attempting to understand both the physics and the device performances based on such SQD structures. Here, lateral carrier transfer among neighboring quantum dots (QDs) has been investigated through spectroscopic measurements for high density InGaAs/GaAs SQDs in a hybrid nanostructure with similar buried QDs (BQDs). Photoluminescence (PL) and temporal-resolved PL (TRPL) spectra demonstrate that the SQDs exhibit intra-layer exciton transfer and also strong carrier transfer to the surface states at 10 K. This imparts different optical characteristics to the SQDs with regards to the band filling and emission-energy-dependent carrier lifetime. In addition, PL excitation (PLE) spectra reveal a wetting layer absorption feature for the SQDs, which provides a channel for thermally activated carriers to transfer among the SQDs and to ultimately escape from the SQD layer. These investigations enrich our understanding of carrier dynamics for InGaAs SQDs, which may help to develop novel surface sensitive sensors.