Limited In incorporation during pseudomorphic InAs/GaAs growth and quantum dot formation observed by in situ stress measurements

In segregation during InAs growth on (0 0 1)GaAs is studied by in situ stress measurements. From the accumulated stress evolution during deposition of 1 ML of In and the ulterior GaAs overgrowth, a limited In incorporation is observed (∼50%). The rest of In is floating or physisorbed on the surface, without contributing to stress through the formation of stable chemical bonds. During overgrowth with GaAs, the In is progressively incorporated as a graded InGaAs layer until total depletion of the floating In layer. This process, very different from Ga/In exchange at the growth front, is strongly temperature dependent for Tg>400 °C. The limited In incorporation gives a new perspective on the self-assembling of quantum dot as the low value for the critical thickness (<1 ML InAs) as well as their formation process.