Abstract
Carrier transfer in vertically-coupled InAs/GaAs quantum dot (QD) pairs is investigated. Photoluminescence (PL) and PL excitation spectra measured at low temperature indicate that the PL peak intensity ratio between the emission from the two sets of QDs—i.e., the relative population of carriers between the two layers of QDs—changes with increasing excitation intensity. Temperature-dependent PL reveals unexpected non-monotonic variations in the peak wavelength and linewidth of the seed layer of QDs with temperature. The PL intensity ratio exhibits a “W” behavior with respect to the temperature due to the interplay between temperature and excitation intensity on the inter-layer carrier transfer.
Highlights
Self-assembled InAs/GaAs quantum dots (QDs) have attracted enormous attention over the past two decades due to their unique characteristics and huge potential for device applications [1,2,3,4,5].In particular, the vertically-stacked InAs/GaAs QDs have been widely applied as a promising structure in many optoelectronic devices, including emitters, infrared detectors, and photovoltaics, as well as devices for optical computations [6,7,8,9,10,11]
From the atomic force microscopy (AFM) images, we found that both layers of QDs had an equal areal density, indicating the possibility that the QDs were vertically aligned into pairs
As the effective mass of the holes is much larger than the electrons, it is expected that carrier tunneling in the InAs bilayer QD structures is primarily performed by the electrons
Summary
Self-assembled InAs/GaAs quantum dots (QDs) have attracted enormous attention over the past two decades due to their unique characteristics and huge potential for device applications [1,2,3,4,5].In particular, the vertically-stacked InAs/GaAs QDs have been widely applied as a promising structure in many optoelectronic devices, including emitters, infrared detectors, and photovoltaics, as well as devices for optical computations [6,7,8,9,10,11]. As a good example, coupling two layers of vertically aligned QDs to fabricate artificial QD-molecules opens a new way to investigate quantum phenomena over a wide range of configurations, and provides an approach to implementing quantum entangled states [12,13,14,15]. Such bilayer QD structures enable flexible manipulation of the quantum coupling between two layers of QDs, independently controlling the QD density, size, and uniformity. Studies of the energy transfer properties are indispensable when attempting to understand the performance of optoelectronic devices based on bilayer InAs/GaAs QD structures
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