Site-selective growth of single quantum dots


  • André Strittmatter

The vision of semiconductor device operation based on quantum mechanical properties of a single quantum dot (SQD) is stimulating many activities towards site-selective growth of quantum dots in order to achieve deterministic device properties. Within the steeply rising field of semiconductor-based quantum optics, in particular, deterministic positioning of single quantum dots makes the key difference which allows to transition from “one-of-a-kind” demonstrators to low-cost mass production. Site-selective quantum dot growth represents however one of the most challenging frontiers for epitaxial growth today as it requires precise control of the lateral assembly of a few thousands of atoms on areas with a spot size not larger than a few tens of nanometers. In order to get a grip onto SQD nucleation various surface patterning technologies have been developed in recent years. Great success has been achieved with nanometer-sized holes patterned on planar substrate surfaces through which single QDs can be positioned with close to 50 nm precision to target coordinates – for example the center of micro-pillar cavities. As shown in the papers by Schneider et al. 1 and Helfrich et al. 2, problems of reduced QD nucleation probability at such holes and degraded QD emission characteristics can be overcome using proper preparation technologies and growth recipes.

Benyoucef et al. 3 take the approach one step further and explore its application to silicon substrates. Very recently, a buried stressor technology for quantum dot positioning on GaAs substrates has been demonstrated which integrates a self-aligned current injection scheme for electrical excitation of single quantum dots 4. Very efficient electrically-driven single photon sources were already demonstrated using such an approach during preparation of this Special Section for physica status solidi. Details of the patterning technologies and the physics of site-selective growth processes are highlighted which makes the reader familiar with the subject and simultaneously covers the state-of-the-art in the field.

André Strittmatter