The sensitivity, of the 2- to 3-dimensional growth transition of InAs self-assembled islands, to the InAs coverage was used to demonstrate the growth of self-aligned InAs islands on etched GaAs ridges by molecular beam epitaxy. The differing migration behaviors of In adatoms on the various crystal planes of etched ridges were used to modulate the supply of In adatoms spatially. The ridges were oriented along the  and [01¯1] directions on (100) substrates with grating spacings of 0.28, 1 or 5µ. Atomic force microscopy revealed that the InAs islands were self-aligned along the ridges and were typically 40nm in diameter and 12nm in height. In samples with -oriented ridges, the islands were located on the side-walls. On the other hand, in the case of [01¯1]-oriented ridges, the islands were on the (100) planes on, and at the foot of, the mesa. On samples with a grating pitch of 0.28µ, all of the islands were located either on the side-walls or at the bottom of the so-called V-groove; for both grating orientations.
D.S.L.Mui, D.Leonard, L.A.Coldren, P.M.Petroff: Applied Physics Letters, 1995, 66, 1620-2