Ground-state exciton emission of InAs quantum dots produced by focused-ion-beam-directed nucleation

We report on scanning micro-photoluminescence measurements on InAs quantum dots that were patterned using an in vacuo focused ion beam. The focused ion beam produced a square array of holes with an array spacing of 2μm, upon which multiple layers of InAs and GaAs were deposited. Two-dimensional mapping of the luminescence spatially and spectrally resolves the emission from individual dots. At some positions, multiple emission peaks are observed, which could have originated from (i) different exciton transitions of the same quantum dot, or (ii) different quantum dots. Power dependence measurements reveal that the emission increases linearly with power, and maps of the emission show that the positions of each peak are spatially separated, suggesting that the peaks are ground-state exciton emission from different dots. ► Single quantum dots are patterned in a 2-dimensional lattice by a focused ion beam. ► Single dot emission linewidth as narrow as 160μeV is observed. ► Spatially mapped photoluminescence gives the site-selective spectrum of the dots. ► A power dependence shows that peaks are from ground-state excitons of different dots.