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BF cross-sectional TEM images of the InAs QDs in (a) sample A, (b) sample B, (c) sample C, and (d) sample D. V-shaped defects are seen in the samples with GaAs cap layer. InAs QDs capped with GaAs layer have a truncated pyramidal shape, whereas the ones capped with layer have a lens shape.
(a) BF cross-sectional TEM image of an InAs QD from sample D with a V-shaped defect. The arrows point to the origins of the defect at the top edges of the truncated pyramidal QD. (b) BF cross-sectional TEM image depicting large coalesced InAs QDs capped with layer from sample C. No defect is observed around the QD. The arrow points to the intersection of two coalesced InAs QDs.
Arrhenius plots of the temperature-dependent integrated PL intensity for samples B and C. (Inset) RT PL spectra of samples B and C.
Details of the QD samples used in this study. Samples A–C were grown on graded substrate while sample D was grown on GaAs substrate and used as a reference.
Compilation of the different values of activation energies as deduced from the temperature-dependent PL measurements. The values of activation energies for the last sample were extracted from Ref. 21. The sample has similar QD structures grown using the same MBE system and the same growth conditions as the samples reported in this study.
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