Residual elastic strains were measured in 2-thick Ga1-xInxAs layers, where x was between 0.07 and 0.14, that had been grown onto GaAs substrates at 625C at a rate of 1/h. The use of X-ray techniques showed that residual strain accounted for 15% of the lattice mismatch. This could not be explained by the difference in thermal expansion coefficients between the substrate and epilayer, but could instead be explained by a reduction in the effective stress; due to repulsive interactions between dislocations. It was also found that increasing the growth temperature from 625 to 670 or 680C did not appreciably change the degree of residual strain. On the other hand, it could be reduced to 5% (or increased to 33%) of the lattice mismatch by decreasing the growth rate from 1 to 0.45/h (or by increasing it from 1 to 2/h). These changes were related to changes in the growth time, since post-growth annealing for 1h at the growth temperature of samples that had been grown at a rate of 1/h led to the same reduction in residual strain as did growth at lower rates. This indicated that, for thick layers, the relaxation process was not complete when growth was interrupted and suggested that, in spite of a large decrease in the effective stress, the dislocations were still mobile.

P.Maigné: Journal of Vacuum Science and Technology A, 1997, 15[1], 43-8