Investigation of strain relaxation mechanisms in InGaAs/GaAs single layer films

In this work a strict comparison of the results obtained on InGaAs/GaAs heterostructures by HRXRD and RBS-channeling analysis shows a discrepancy in the In atomic fraction determined by the two techniques. The discrepancy leads to a difference in the reference lattice parameter of the relaxed film and, therefore, changes the description of the strain relaxation rate. After a discussion on the possible reasons for this discrepancy, the results have been interpreted as the influence of the atomic degrees of freedom internal to the lattice unit cell which could determinate the equilibrium shape of the unit cell. While it has been not strictly proved, the most reasonable hypothesis to explain the experimental results is that local ordering leads to a relaxed unit cell which is slightly tetragonal.