Impact of dislocations in InAs quantum dot with InGaAs strain-reducing layer structures on their optical properties

Abstract

InAs quantum dots with InGaAs strain-reducing layer on GaAs(001) grown at three different temperatures were investigated from the aspect of both structural and optical properties. Dislocations originated from the InAs quantum dot (QD) layer were observed at growth temperatures of 490 °C, 500 °C, and 510 °C. Their densities are relatively larger in the cases of 490 °C and 510 °C, where they are caused by strain accumulation at larger-size InAs quantum dots during cover layer growth. Photoluminescence lifetimes at 6 K are almost the same in the three samples. On the other hand, that of the 500 °C-grown sample is an order of magnitude larger than the other two samples at 300 K. This indicates that dislocations act as a non-radiative center to deteriorate optical characteristics. Growth around 500 °C suppresses the growth of larger-size InAs QDs and reduces the InAs strain accumulation, which leads to the dislocation formation at the cover layer.

Impact of low-temperature cover layer growth of InAs/GaAs quantum dots on their optical properties

“…25) The sample grown at 510 °C whose dislocation density was the highest showed the lowest photoluminescence (PL) intensity compared to the 490 °C and 500 °C grown samples. 25) However since 510 °C is the highest growth temperature, the quality of the InAs QDs themselves can be high. Therefore, reducing the dislocations in the 510 °C grown sample has the possibility of further improving the optical quality.…”

“…So far, we have investigated the effect of the growth temperature of InAs QDs on the optical properties in an InGaAs SRL adapted QD structure. 25) The dislocations in GaAs SL formed directly above InAs QDs act as a nonradiative recombination center to deteriorate their optical qualities. 25) The sample grown at 510 °C whose dislocation density was the highest showed the lowest photoluminescence (PL) intensity compared to the 490 °C and 500 °C grown samples.…”

“…25) The dislocations in GaAs SL formed directly above InAs QDs act as a nonradiative recombination center to deteriorate their optical qualities. 25) The sample grown at 510 °C whose dislocation density was the highest showed the lowest photoluminescence (PL) intensity compared to the 490 °C and 500 °C grown samples. 25) However since 510 °C is the highest growth temperature, the quality of the InAs QDs themselves can be high.…”

“…In this study, to explore the mechanism of dislocation formation and its suppression method leading to the improvement of optical quality in InAs QD structure, the effect of growth temperature and thickness of the LT InGaAs/GaAs cover layer on the optical quality of InAs QD structure were investigated under the InAs QDs fixed growth temperature of 510 °C where it was found that there existed relatively high dislocations in the previous study. 25) PL intensity was largely influenced by the growth condition of the LT cover layer. PL intensity decreased as the number of dislocations formed above InAs QDs increased.…”

“…Figure 1 shows the schematic QD structure grown in this study, where it is the same as described in Ref. 25. After the removal of surface oxide in the MBE chamber, an 8-layer-stacked InAs QD structure sandwiched with AlGaAs cladding layer was formed on GaAs(001) substrate.…”