An investigation was made of elliptical surface defects on GaAs layers which had been grown, by means of molecular beam epitaxy, on GaAs substrates. The presence of microscopic defects in GaAs substrates, as revealed by AB etching, was not essential for the formation of surface defects of this type. They were convex to the epilayer surface and had one dislocation with a screw component near to each of the centers. The results indicated that they originated in threading dislocations from the GaAs substrates, and were probably formed by spiral growth. The effects of growth rate and substrate misorientation upon the elliptical defects were also studied. As the growth rate increased, the size of the defects became smaller, and they disappeared at a growth rate of 4/h. They were not formed on substrates which were oriented 2° off (100) and towards <110>.

S.Takagishi, H.Yao, H.Mori: Journal of Crystal Growth, 1993, 129[3-4], 443-8