Abstract
The electronic coupling in vertically aligned InAs/GaAs quantum dot (QD) pairs is investigated by photoluminescence (PL) measurements. A thin Al0.5Ga0.5As barrier greatly changes the energy transfer process and the optical performance of the QD pairs. As a result, the QD PL intensity ratio shows different dependence on the intensity and wavelength of the excitation laser. Time-resolved PL measurements give a carrier tunneling time of 380 ps from the seed layer QDs to the top layer QDs while it elongates to 780 ps after inserting the thin Al0.5Ga0.5As barrier. These results provide useful information for fabrication and investigation of artificial QD molecules for implementing quantum computation applications.
Highlights
Many investigations have addressed the fabrication, characterization, and exploitation of selfassembled InAs/GaAs quantum dot (QD) structures due to their unique properties as well as their great potential for various optoelectronic devices [1,2,3,4,5,6,7,8]
The AFM images indicate that SQDs formed by 2.0 ML of InAs have an average diameter of 68.5 ± 6.3 nm and an average height of 11.7 ± 1.5 nm with an areal density of 5.6 × 109 cm−2, whereas the top layer of QDs (TQDs) formed by 2.6 ML of InAs have an average diameter of 83.0 ± 6.3 nm and an average height of 19.3 ± 1.5 nm, with an areal (a)
Low-temperature PL measurements show that the QD peaks shift to the blue and the relative PL intensities of the two QD layers change as a result of adding the AlGaAs barrier
Summary
Many investigations have addressed the fabrication, characterization, and exploitation of selfassembled InAs/GaAs quantum dot (QD) structures due to their unique properties as well as their great potential for various optoelectronic devices [1,2,3,4,5,6,7,8]. The fabrication of quantum coupled InAs/GaAs QD pair structures is implemented by growing two layers of InAs QDs with a thin GaAs spacer to form vertically aligned QD pairs Such bilayer InAs/GaAs QD structures enable tuning of the quantum coupling between InAs/GaAs QDs by adjusting the GaAs spacer thickness and provide flexibility to independently control the QD density and size as well as to improve QD uniformity [16,17,18,19]. These advantages make the vertically aligned InAs/GaAs QD pair structure an interesting choice for
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