Density limits of high temperature and multiple local droplet etching on AlAs

Abstract The density of nanoholes created by self-assembled Al droplet etching of AlAs surfaces during molecular beam epitaxy is studied. We find a clear decrease of the hole density with increasing etching temperature T up to a threshold temperature T = 620 ° C . At T > 620 ° C , the hole density saturates at a minimum of 2 × 10 8 cm − 2 . We attribute this saturation to a change of the AlAs surface reconstruction. On the other hand, at reduced T , hole densities up to 2 × 10 9 cm − 2 have been achieved. However, this hole density increase is accompanied by a reduction of the hole depth. To generate high density holes with larger depth suited for quantum dot fabrication, we have studied the effect of repeated etching steps.