A detailed correlation was established between the threading dislocation density, residual stresses, and the growth area of striped and square mesas of molecular beam epitaxially grown 3-thick GaAs on pre-patterned Si and post-patterned 3-thick GaAs on Si. The morphologies and distributions of dislocations were also compared for samples, which were between 1 and 100 in width, as observed before and after annealing using cross-sectional transmission electron microscopy. Micro-photoluminescence measurements revealed that the residual stress in the patterned GaAs decreased with decreasing mesa size; especially for sizes of less than 25, regardless of the patterning method and the shape of the samples. However, no clear reduction in the dislocation density was observed in as-grown layers on pre-patterned stripe and square Si mesas that were smaller than 10. On the other hand, the defect density in layers which had pattern sizes of less than 4 was higher than that in layers with sizes that were greater than 10; due to the additional generation of micro-twins and stacking faults from the (111) faceted regions which formed at the sides, along the <110> directions of the grown films. Annealing treatments (900C, 10s) effectively reduced the density of these latter defects in patterned films, using both pre- and post-patterning procedures; regardless of the pattern sizes. However, no clear decrease in the dislocation density was detected in small-sized patterns of less than 10. This behavior was also observed for post-patterned samples which included thin Si insertion layers in the GaAs films. The results strongly suggested that thermal expansion mismatch stresses did not cause any further dislocation generation during cooling from the growth temperature to room temperature. The dislocations were generated during growth, due to lattice mismatch-induced stress.

M.Tamura, A.Hashimoto, J.Kasai, A.Nishida: Journal of Crystal Growth, 1995, 147[3-4], 264-73