InAs self-assembled quantum dots (QDs) were grown on Si (001) substrates via molecular beam epitaxy. The size distribution and density of InAs QDs grown under different conditions were studied using plan-view transmission electron microscopy. Dot density was shown to strongly depend on arsenic beam equivalent pressure (BEP) ranging from 2.8 X 10(-5) to 1.2 x 10(-3) Pa. In contrast, dot density was nearly independent of substrate temperature from 295 to 410 degrees C under constant arsenic BEP, while broadening of size distribution was observed with increasing temperature. The mechanism accounting for some of the main features of the experimental observations is discussed. Finally, InAs quantum dots with optimized narrow size distribution and high density were grown at low arsenic BEP of 7.2 X 10(-5) Pa and low temperature of 250 degrees C followed by annealing at arsenic BEP of 1.9 X 10(-4) Pa and temperature of 410 degrees C. (c) 2005 Elsevier B.V. All rights reserved.