Spoluautoři ZÍKOVÁ Markéta, HOSPODKOVÁ Alice, PANGRÁC Jiří, OSWALD Jiří, HULICIUS Eduard

Semiconductor quantum dots (QDs) are objects with all three dimensions comparable to the Bohr radius of Wannier exciton. If prepared from InAs on the GaAs substrate, they can reach luminescence in region 1300 and 1550 nm, which is very promising for the silica low-loss fibres. Reaching these wavelengths can be easier when covering the QDs by GaAsSb strain reducing layer (SRL). We have studied InAs/GaAs QDs prepared by the Metalorganic Vapour Phase Epitaxy in Stranski-Krastanow self-organized growth mode at temperature 510°C and covered by GaAsSb SRL. This SRL reduces the strain inside QDs, conserves their height and shape and prevents dissolution of QDs. SRL also changes the electron and hole localization depending on the amount of Sb in GaAsSb. The holes may be localized in the QD (type I heterostructure, less than about 14 % of Sb) or outside the QD in the SRL (type II, more than 14 % of Sb); the electrons are in both cases inside the QD. We found out that for higher growth temperature (510°C) the Sb incorporation into the SRL is decreased. Two explanations are suggested: first, higher strain on the apex of bigger QDs, and second, increased amount of not-inbuilt Sb on the surface. However, unincorporated surfacting Sb atoms also prevent QD dissolution. Increased QD size together with decreased Sb incorporation helped us to obtain type I QD structure with long wavelength emission at 1400 nm.