Closely stacked multilayer structures of InAs islands with intermediate-layer thicknesses d of 3, 6, 10, and 20 nm were grown by the Stranski-Krastanow mode of molecular beam epitaxy and were observed using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The multilayers consisted of five InAs layers' each of a thickness of 1.8 monolayers and four GaAs layers each of a thickness d. Columns of coherent islands were observed by cross-sectional TEM. Changes in the size and density of the islands with d, determined by AFM, could be explained in terms of (i) change in the vertical pairing probability of islands, (ii) detachment of In from the top of the island, and (iii) surface segregation of In. The observed AFM images of the islands were elliptical. Their major axis was in the [ 110] direction, and the length of the minor axis was 80% of that of the major axis. (C) 2003 American Vacuum Society.