Shape changes in the capping process of low density InAs quantum dots (QDs) with a thin GaAs layer under As4 and As2 conditions were investigated by atomic force microscopy. The shapes of the capped QDs differ considerably depending on the used arsenic source, As4 or As2. In the case of the As4 source, the QD shape elongated along the [(1) over bar 10] direction with the increase in the capping temperature, whereas the elongation along the [(1) over bar 10] direction is small compared to that along the [(1) over bar 10] direction. On the other hand, in the case of As2, the elongation along the [(1) over bar 10] direction is lesser than that in the As4 case. In addition, the elongation along the [110] direction is promoted even at a low capping temperature. In the case of As2, isotropic capping of the QDs can be achieved at a higher capping temperature compared to the case using As4. (c) 2013 Elsevier B.V. All rights reserved.