  We report on photoluminescence measurements of vertically stacked InAs/GaAs
quantum dots grown by molecular-beam epitaxy on focused ion beam patterned hole
arrays with varying array spacing. Quantum dot emission at 1.24 eV was observed
only on patterned regions, demonstrating preferential nucleation of
optically-active dots at desired locations and below the critical thickness for
dot formation at these growth conditions. Photoluminescence measurements as a
function of varying focused ion beam irradiated hole spacing showed that the
quantum dot emission intensity increased with decreasing array periodicity,
consistent with increasing dot density.
