Molecular beam epitaxial growth of site-controlled InAs quantum dots on pre-patterned GaAs substrates

Ex situ electron-beam lithography followed by conventional wet etching has been used to pattern small holes 60-150 nm wide, similar to 13 nm deep in GaAs substrates. These holes act as preferential nucleation sites for InAs dot growth during subsequent overgrowth. By varying either the InAs deposition amount or the thickness of a GaAs buffer layer, the occupancy over the patterned sites can be controlled. Comparison with growth on a planar substrate shows that preferential nucleation occurs due to a reduction in the apparent critical thickness above the pattern site; the magnitude of this reduction is dependent on the dimensions of the initial pattern. (c) 2006 Elsevier Ltd. All rights reserved.