Emission characteristics of shape-engineered InAs/InAlGaAs quantum dots subjected to thermal treatments

We indirectly evaluated the inter-diffusion behaviors of group-III elements at the interface between shape-engineered (SE)-InAs/In_0.52Al_0.24Ga_0.24As quantum dots (QDs) and In_0.52Al_0.24Ga_0.24As (InAlGaAs) barriers by investigating the optical properties. Rapid thermal annealing (RTA) was carried out for five stacks of SE-InAs/InAlGaAs QDs separated by an InAlGaAs spacer under temperatures ranging from 650 to 800 ° C. The emission wavelength of the SE-QDs subjected to thermal treatment was red-shifted from that for the as-grown QDs. For a RTA temperature of 700 ° C, the emission wavelength was measured to be 1507 nm at room temperature (RT), which was red-shifted by 3 nm compared to that of the as-grown sample (1504 nm). At an annealing temperature of 800 ° C, the emission wavelength was 1506 nm, which is still longer than that of the as-grown sample. This behavior is quite different from that of an InAs/GaAs QD system. The RT photoluminescence (PL) yield of the SE-InAs/InAlGaAs QDs subjected to thermal treatment was first enhanced at temperature up to 700 ° C and then decreased slightly with further increasing RTA temperature. The PL intensity of the QDs for a RTA temperature of 700 ° C was 8.8 times stronger than that of the as-grown sample.