Comparison of quantum well intermixing in GaAs structures using a low temperature grown epitaxial layer or a SiO2 cap

Studies of quantum well intermixing (QWI) have been performed on Al-free GaAs based structures in which InGaAs quantum wells (QWs) have either GaAs barriers or InGaAsP quaternary barriers such that the barrier-QW compositional change consists solely of a group III change (GaAs barrier) or a group V change (quaternary barrier). These structures permit identification of the sublattice upon which intermixing occurs when the point defects responsible for the QWI are created by annealing in the presence of a (conventional) dielectric (SiO2) cap layer versus an InGaP cap layer grown at low temperature (LT-InGaP). QWI occurs on the group III sublattice via vacancy diffusion in both the LT-InGaP and SiO2 capped samples with identical group V compositions in the QW and barrier layers. For the samples with identical group III compositions for the QW and barriers, QWI is only observed with the LT-InGaP capping and occurs via group V interstitial diffusion and P–As exchange in the QW.