Well-aligned InAs quantum dot (QD) arrays are successfully grown on a GaAs ridge structure with a top facet width of 300 nm by using an AS(2) source. InAs QDs array at the center of a GaAs ridge by using an AS(2) source, while QDs are grown all over a ridge surface by using an AS(4) source. This is due to different crystal facets that formed on GaAs ridge structures. GaAs ridge-top structure grown with an AS(2) source has V-grooves consisting of (4 1 1)A surfaces, and QDs are grown at the bottom of V-grooves. The ridge structure grown with an AS(4) source has (1 0 0)-like surfaces, and QDs are grown on (1 0 0) surface irregularly. InAs QDs on a patterned area have good optical properties with a full-width at half-maximum of 40 meV. (c) 2006 Elsevier B.V. All rights reserved.