INVESTIGATION OF STRAIN RELAXATION MECHANISMS IN INGAAS GAAS SINGLE-LAYER FILMS/

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