Strain study of self-assembled InAs quantum dots by ion channeling technique.

Ion channeling technique using MeV C⁺⁺ ions was used to study strain in self-assembled InAs quantum dots (QDs) buried in GaAs matrix. Because of the use of heavy ions, we were able to observe an angular shift in the angular scan of the In signal relative to that of the Ga/As signal. This provided a direct evidence that the InAs lattice is larger than that of GaAs in the growth direction. Combining the channeling results in [100] and [110] directions and the photoluminescence emission spectrum, we conclude that the InAs QDs are under tensile strain in the growth direction and have the same lattice constant as that of GaAs in the lateral direction. Thermal annealing causes the strain to relax, first in the growth direction and then in the lateral direction as the annealing temperature increases. The photoluminescence spectra of the QDs before and after annealing indicate, however, that composition intermixing also takes place during annealing and is the dominant factor in determining the band gap energy of the QDs. [ABSTRACT FROM AUTHOR]