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Independent wavelength and density control of uniform GaAs/AlGaAs quantum dots grown by infilling self-assembled nanoholes
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View: Figures


Image of FIG. 1.
FIG. 1.

(a) Nanohole density (n) vs. Ga rate (F), for 3 ML excess Ga, deposited continuously (black solid symbols, error bars indicating density variation across a single sample), or as 19 pulses of 1(2.5) s Ga/0.5 s GaAs at 0.5(0.25) ML/s Ga (red open symbols, error bars indicate the density spread over samples). Solid lines are linear fits to the data, dotted lines are fits using where . (b) AFM images of nanoholes fabricated using 3 ML Ga at different rates. The white circles depict the calculated initial Ga droplet size. (c) Average AFM linescans (average of 10–15 holes) in the [110] and [] directions of nanoholes fabricated with different Ga rates and amounts. (d) Comparison of the initial droplet height (radius) with final hole depth (width) in the left (right) panel for different Ga deposition amounts and rates (both continuous and pulsed). Hole dimensions are defined with respect to the planar regions outside the holes.

Image of FIG. 2.
FIG. 2.

(a) Ensemble photoluminescence from a nominally 1 nm thick QD. (b) Single dot spectrum showing neutral and charged exciton lines, inset showing orthogonally polarised exciton emission. (c) Frequency histograms of neutral exciton energy of 100 (50) dots nominally 3.5 nm (0.5 nm) thick.

Image of FIG. 3.
FIG. 3.

(a) AFM images of a nanohole at different stages of QD growth. (b) Average AFM linescans (average of over 10 holes) showing the nanohole profile: as-etched (black), after overgrowth of 7 nm (green), 0.5 nm GaAs (blue), 1.5 nm GaAs (orange dashed), and after capping by 80 nm and 20 nm GaAs (black dotted). The shaded region shows the volume of a nominally 0.5 nm GaAs QD. (c) PL of QD ensembles (obtained by summing micro-PL spectra taken at different points) with different nominal GaAs thicknesses, spectra offset vertically for clarity. (d) Graph showing the QD emission energy (solid symbols) and the calculated QW thickness, where the QW has the same emission energy as the QD (open symbols) vs. nominal GaAs thickness. The square symbols correspond to QDs in nanoholes with the shape shown in (b). The circular symbols correspond to QDs in a shallower nanohole as shown in Fig. 1(c). The curves are modelled using the initial nanohole profile and assuming all the GaAs deposited on the hole ends up at the hole bottom, as described in the text, and as depicted by the schematic diagram in (d).


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Independent wavelength and density control of uniform GaAs/AlGaAs quantum dots grown by infilling self-assembled nanoholes