Highly versatile ultra-low density GaAs quantum dots fabricated by filling of self-assembled nanoholes

GaAs quantum dots (QDs) of ultra-low density (ULD) are fabricated by filling of nanoholes in AlGaAs surfaces. The holes are drilled using self-assembled local droplet etching with Al droplets. By precisely controlling the arsenic flux and the substrate temperature, the QD density is reduced down to the 106 cm−2 range uniformly over the whole wafer. The QD size is precisely adjustable via the hole filling level. By this, the optical emission energy of the QDs can be adjusted over a wide energy range of at least 120 meV. The surface visibility of ULD QDs allows their simple integration into lithographic processing.