Residual strain measurements in thick InxGa1−xAs layers grown on GaAs (100) by molecular beam epitaxy

The final stages of strain relief in the lattice mismatched InxGa1−xAs/GaAs(100) system are addressed by the examination of the residual strain in thick films (∼3 μm), grown by molecular beam epitaxy, across the entire compositional range. These results are compared with the observed variations in both the growth mode and material quality, and related to available theories. It is found that measurements are not consistent with a degradation of material quality that is simply misfit dependent, or to an abrupt change from two-dimensional (2-D) to three-dimensional (3-D) growth in the relaxation stage. Instead, the results seem to be more consistent with a continuous change from 2-D to 3-D growth between x=0 and x=0.4 (it is wholly 3-D above x=0.4). In addition, the large residual strains observed around x=0.5 are related to the poor material quality (possibly through work hardening) at this composition, which is in turn due to problems peculiar to the growth of mismatched alloys.