Formation of self-assembled InAs 3D islands on GaAs (1 1 0) substrate by metal organic vapor phase epitaxy has been investigated. Relatively uniform InAs islands with an average areal density of 109 cm−2are formed at 400 href="/science?_ob=MathURL&_method=retrieve&_udi=B6THY-4PG86X6-8&_mathId=mml18&_user=10&_cdi=5295&_rdoc=34&_acct=C000050221&_version=1&_userid=10&md5=9fcff1bbd1ae1db2510ef49a6e8f28a7" title="Click to view the MathML source">° C using a thin InGaAs strain reducing (SR) layer. No island formation is observed without the SR layer. Island growth on GaAs (1 1 0) is found to require a significantly lower growth temperature compared to the more conventional growth on GaAs (1 0 0) substrates. In addition, the island height is observed to depend only weakly on the growth temperature and to be almost independent of the V/III ratio and growth rate. Low-temperature photoluminescence at 1.22 eV is obtained from the overgrown islands.