Linear arrays of InGaAs quantum dots on nanostructured GaAs-on-Si substrates

Linear arrays of high-quality quantum dots (QD) integrated in Si are an ideal platform in exploring the manipulation and transmission of quantum information. Understanding QD self-organization mechanisms on substrates compatible with Si technology is therefore of great practical importance. Here we demonstrate the epitaxial growth of linear arrays of InAs and InGaAs QDs from As2 and In molecular beams on bare and GaAs-coated Si(0 0 1) substrates, patterned by high-resolution laser interference nanolithography. Atomic force microscopy, in combination with high-resolution scanning and transmission electron microscopies, show that these arrays exhibit an improvement in growth selectivity, lateral order and size uniformity of the QDs when a pseudomorphic 1 nm-thick GaAs buffer layer is grown prior to InAs deposition. In addition, preferential nucleation of InxGa1-xAs QDs along the 〈1 1 0〉 -oriented edges of the nanostructured GaAs-on-Si(0 0 1) substrate results from In adatom migration from (1 1 1) to (0 0 1) nanofacets and the erosion of the wetting and buffer layers caused by the Ga-In intermixing at the step edge during the Stranski-Krastanov transition. These are key elements in the formation of linear arrays of coherent QDs, which differ in morphology and structure from those obtained on both GaAs(0 0 1) and Si(0 0 1) planar surfaces.

Linear arrays of InGaAs quantum dots on nanostructured GaAs-on-Si substrates Articles