The influence of an AlAs cap layer with a thickness of a few monolayers on the optical properties of molecular beam epitaxy-grown InAs/GaAs self-assembled quantum dots is investigated. The capping of the InAs islands with a thin AlAs layer before the overgrowth by GaAs leads to a blueshift of the photoluminescence at a substrate temperature TS=480 °C, but to a significant redshift at TS=530 °C. This indicates that the InAs/GaAs intermixing caused by In segregation at TS=530 °C can be considerably reduced by a thin AlAs capping layer. This leads to deeper potential wells due to the higher In content in the quantum dots which results in a room-temperature photoluminescence at about 1.3 μm.
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Arzberger et al. (1999) studied this question.