Self-organized anisotropic strain engineering for lateral quantum dot ordering

Lateral ordering of semiconductor quantum dots (QDs) of high quality in well-defined arrangements is essential for the realization of future quantum functional devices with applications in solid state quantum computing and quantum communication [1]. We have developed a new concept for the creation of laterally ordered QD arrays by self-organized epitaxy. The concept is based on self-organized anisotropic strain engineering of (In,Ga)As/GaAs superlattice (SL) templates by molecular beam epitaxy (MBE) and the lateral ordering of (In,Ga)As QDs by local strain recognition. It is demonstrated for one-dimensional (1D) and two-dimensional (2D) QD arrays on planar GaAs (100) [2] and (311)B [3] substrates. Starting from a nanoscale, random (In,Ga)As QD layer, thin GaAs capping, annealing, GaAs overgrowth, and repetition in SL growth produces highly ordered 1D and 2D (In,Ga)As and, thus, strain-field modulations on a mesoscopic length scale. SL self-organization is governed by surface reconstruction and strain induced anisotropic surface migration together with lateral and vertical strain correlation.When (In,Ga)As QDs are grown on the strain modulated SL templates, they arrange into well-ordered, straight 1D multiple and single QD arrays on GaAs (100), and into a lattice of ordered lateral QD molecules with controlled QD number and single QDs on GaAs (311)B.