Focused ion beam modification of surfaces for directed self-assembly of InAs/GaAs(001) quantum dots

Controlled nucleation of InAs quantum dots has been achieved by Ga + focused ion beam modification of GaAs(100) surfaces. Quantum dots may be induced in irradiated regions despite the fact that the deposited thickness is less than the critical thickness for their formation under typical growth conditions when the ion dose is greater than 10 13 ions cm −2 . We also find that the dot density increases with increasing ion dose, and reaches saturation for D >10 14 ions cm −2 . Parameters such as dot height and diameter are unaffected by the dose level. Thus, we show that the increase in dot density is a result of diffusion of adatoms from outside the patterned region. The mechanism for enhanced quantum dot formation is due to the formation of monolayer deep holes created in the substrate by the ion beam, which may be used to form regular arrays of quantum dots.