Impurity-free disordering of InAs/InP quantum dots

Abstract

Impurity-free disordering (IFD) of the InAs quantum dots (QDs) capped with either an InP layer or an InGaAs∕InP bilayer is studied. The samples are coated with a SiO₂ or TiO₂ dielectric layer followed by rapid thermal annealing at 700, 750, 800, and 850°C for 30s . A large differential energy shift of 157meV is induced by SiO₂ in the QDs capped with an InGaAs∕InP bilayer. Contrary to the reported results on the suppression of intermixing of GaAs based QDs by TiO₂ , the authors find that intermixing of InAs∕InP QDs is promoted by TiO2 . X-ray photoelectron spectroscopy depth profiles show that both In and P outdiffuse to a TiO₂ layer whereas Ga, In, and P outdiffuse to a SiO₂ layer leading to different degrees of intermixing. The results indicate that a group V interstitial diffusion mechanism might be responsible for IFD of InAs∕InP QDs.