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(a) AFM image of the uncapped GaSb/GaAs QDs. (b) and (c) Histograms of the QD diameter and height size distributions, respectively, for the uncapped QDs.
PL taken at 10 K and 424.5 μW of the GaSb/GaAs QDs showing the GaAs substrate peak at 1.49 eV, the WL peak at 1.36 eV, and the QD peak centered between 1.1 and 1.22 eV. The solid and dashed red arrows indicate the peak positions calculated for large compact QDs (1.155 eV) and small, disintegrated islands (1.220 eV) using an 8-band k.p method where approximate nanostructure dimensions are taken from the APT data. The inset shows the recombination pathways for the GaSb QDs, GaSb WL, and GaAs.
XSTM images of the GaSb/GaAs nanostructures looking at (110) surfaces showing (a) a compact QD, (b)–(e) clusters of smaller islands with varying separation and degrees of As-Sb intermixing between the islands.
(a) Three-dimensional image of one of the APT volumes showing only Sb atoms. Yellow iso-concentration surfaces highlight areas with 9% Sb concentration. (b)–(e) Contour plots of varying Sb concentration composed from a slice through the center of the nanostructures as analyzed by APT. The concentration scale is the same for each plot. A voxel size of 0.5 × 0.5 × 0.5 nm3 and a delocalization distance of 3 nm were used. Sb concentrations are displayed in color from darker (lower%Sb) to lighter (higher%Sb). Higher concentrations shown in the compact QD in (c) are displayed in white with black contour lines. Note that (d) contains two side-by-side clusters of small islands. (f) and (g) Cross-sectional views along a given x-z plane taken from (e). (1), (2), and (3) are described in Figure 5 . All scale bars are 5 nm.
Line profiles of Sb concentration measured through the center of the nanostructures at locations (1), (2), and (3) in Figures 4(c) and 4(e) using a cylinder with a diameter of 1.5 nm and a 1.5 nm bin width. The dashed line in each plot is a guide to the eye.
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