Investigation of Strain Relaxation Mechanisms in InGaAs/GaAs Single Layer Films

Abstract

Abstract. 2014 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.

Selective ion-channeling study of misfit dislocation grids in semiconductor heterostructures: Theory and experiments

“…It has been demonstrated that RBS channeling and x-ray diffraction provide measurements of the tetragonal distortion of an epitaxial layer in perfect agreement. 30,31 In the case of RBS channeling, in order to obtain the in-plane strain ʈ the relation between ʈ and the perpendicular strain Ќ arising from the isotropic elastic continuum model is assumed. 29 However, there are experimental data that contradict this assumption.…”

“…29 However, there are experimental data that contradict this assumption. 28,31 One possible explanation is related to the conservation of the bond lengths and to the consequent deformation of the angles between anion and cation bonds leading to significant deviations from the ideal zinc-blende lattice, particularly under epitaxial conditions. These ''internal'' degrees of freedom can give rise to a lower elastic energy density per unit volume and consequently to a lower tetragonal distortion 32 than is predicted in the frame of the virtual crystal approximation.…”