III/V ratio based selectivity between strained Stranski-Krastanov and strain-free GaSb quantum dots on GaAs

The authors demonstrate and characterize type-II GaSb quantum dot (QD) formation on GaAs by either Stranski-Krastanov (SK) or interfacial misfit (IMF) growth mode. The growth mode selection is controlled by the gallium to antimony (III/V) ratio where a high III/V ratio produces IMF and a low ratio establishes the SK growth mode. The IMF growth mode produces strain-relaxed QDs, where the SK QDs remain highly strained. Both ensembles demonstrate strong room temperature photoluminescence (PL) with the SK QDs emitting at 1180nm and the IMF QDs emitting at 1375nm. Quantized energy levels along with a spectral blueshift are observed in 77K PL. Transmission electron microscope images identify the IMF array and crystallographic shape for both types of QD formation. Atomic force microscope images characterize QD geometry and density.