We investigated the self-assembly of GaAs/AlGaAs quantum dots (QDs) on GaAs (3 1 I)A substrates by droplet epitaxy. High-density Ga droplets were formed on the (3 11)A surfaces due to the short surface migration distance of Ga atoms. The maximum area density exceeded 10(11)/cm(2). These Ga droplets were crystallized into dot-shaped nanostructures (QDs) even by the irradiation of low As-4 flux intensity. The capped GaAs QDs exhibited efficient, narrow PL emission at 5K, indicating their high quality and uniformity. (C) 2008 Elsevier B.V. All rights reserved.