Influence of a thin AlAs cap layer on optical properties of self-assembled InAs/GaAs quantum dots

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 T-S=480 degrees C, but to a significant redshift at T-S=530 degrees C. This indicates that the InAs/GaAs intermixing caused by In segregation at T-S=530 degrees 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 mu m. (C) 1999 American Institute of Physics. [S0003-6951(99)02751-5].