Type-I to Type-II Transformation of Hybrid Quantum Nanostructures

Hybrid nanostructures of type-I InAs quantum dots (QDs) and type-II GaSb quantum rings (QRs) separated by a GaAs spacer layer is experimentally demonstrated in this paper. As the thickness of GaAs spacer layer decreases, the dot density increases with the reduced dot height, indicating that the smaller InAs QDs tend to grow atop and along the rims of GaSb QRs. With a thin GaAs spacer of 2 nm, the photoluminescence of hybrid nanostructures at room temperature is redshifted to 1.4 μm and remains bright at room temperature. This phenomenon suggests that the electrons in InAs QDs and holes in GaSb QRs recombine radiatively with high quantum efficiencies as the two nanostructures are nearby. The longer carrier lifetime is also observed from the hybrid nanostructures which keep electrons and holes farther, confirming the nature of type-II transitions in these hybrid nanostructures.