Post-growth annealing of type-II GaSb/GaAs quantum dots grown with different V/III ratios

We report the influence of V/III beam-equivalent-pressure ratios and post-growth annealing on the photoluminescence of GaSb quantum dots grown on GaAs(1 0 0) by molecular beam epitaxy. Increasing the V/III beam-equivalent-pressure ratio from 3 to 5 and then to 7 results in decreased photoluminescence intensity and redshifts the photoluminescence wavelength. The post-growth annealing blueshifts the quantum dot photoluminescence emission and decreases the full-width-at-half-maximum of the photoluminescence peak when annealing temperature is increased above 800 °C. The blueshift behavior is found to be independent on the V/III ratios indicating a similar atomic interdiffusion mechanism for all investigated samples regardless of the quantum dot properties. The photoluminescence intensities of the three samples experience an increase after moderate annealing. Whereas the intensity of the sample with the highest V/III ratio further increases, the intensity of the sample with lower V/III ratios decreases again upon higher annealing steps above 900 °C. Furthermore, temperature- and power dependent photoluminescence measurements are performed on as-grown and 870 °C annealed samples with V/III ratios of 3 and 7 in order to study the reduced quantum dot confinement in more detail.

► Increasing V/III (Sb/Ga) ratio results in larger quantum dots with rectangular shape.
► Quantum dots grown with larger V/III ratio emits light at lower energy and intensity.
► Blueshift and decrease in peak width occurs when samples are annealed above 800 °C.
► Blueshift behavior is found to be independent on the V/III ratios.
► Smaller V/III ratio and thermal annealing reduces band offset for holes.