Control of Optical Emission from Coupled Excitonic States in Quantum Dot Superlattice Structures

Multilayered self-assembled quantum dot (SAQD) structures are indispensable for increasing the SAQD density in practical device applications. The electronic and optical natures of these structures are affected by the spacer-layer thickness; the electronic states in SAQDs can couple vertically with decreasing the thickness. We have confirmed the control of optical emission from such coupled SAQDs, which form a SAQD-superlattice structure. The transverse-magnetic mode of photoluminescence (PL) from the coupled SAQD has been found to be enhanced. The detailed PL analyses have shown bimodal effective size distribution consisting of coupled and uncoupled SAQDs. Also, the relaxation time of the coupled SAQDs has been shown to be longer than that of the uncoupled SAQDs. The present coupled SAQD structure will provide a useful technique of controlling SAQD emission properties.