The formation of InAs quantum dots by Stransky-Krastanow method on (311)B InP substrates has been studied. On Al0.48In0.52As alloy lattice matched on InP, large changes of the quantum dot structural characteristics have been observed as a function of the amount of InAs deposited and of the arsenic pressure during the InAs quantum dot formation. Small quantum dots (minimum diameter = 20 nm) in very high density (1.3 x 10(11) quantum dots per cm(2)) have been achieved in optimized growth conditions. These results are interpreted from the strong strain field interaction through the substrate at high density and from the InAs surface energy evolutions with the Arsenic pressure. The effect on quantum dot characteristics of the arsenic pressure during the growth of Al0.48In0.52M buffer layers has also been investigated. Despite the importance of this parameter on the Al0.48In0.52As clustering, weak changes have been observed. (c) 2006 Elsevier B.V. All rights reserved.