Self-organized lattice of ordered quantum dot molecules

Abstract

Ordered groups of InAs quantum dots (QDs), lateral QD molecules, are created by self-organized anisotropic strain engineering of a (In,Ga)As∕GaAs superlattice (SL) template on GaAs (311)B in molecular-beam epitaxy. During stacking, the SL template self-organizes into a two-dimensionally ordered strain modulated network on a mesoscopic length scale. InAs QDs preferentially grow on top of the nodes of the network due to local strain recognition. The QDs form a lattice of separated groups of closely spaced ordered QDs whose number can be controlled by the GaAs separation layer thickness on top of the SL template. The QD groups exhibit excellent optical properties up to room temperature.

Increase of charge-carrier redistribution efficiency in a laterally organized superlattice of coupled quantum dots

“…Thus, a periodic organization appears in the QD plane, in order to minimize the surface energy. 16 In multiply stacked layers this organization is enhanced by the strain field induced by the first QD layer. This has been demonstrated by Tersoff et al who modeled the stress field in stacked QDs.…”

Single InAs quantum dot arrays and directed self-organization on patterned GaAs (311)B substrates

“…The natural ordering of the QD arrays is created by self-organized anisotropic strain engineering of InGaAs/GaAs superlattice ͑SL͒ templates. 5,6 InGaAs QD growth, thin GaAs capping, anisotropic adatom surface migration during annealing, GaAs separation layer growth, and strain correlated stacking produces a two-dimensional ͑2D͒ lateral strain field modulation ͑of shallow 2D strain induced nodes͒ on the SL template surface governing InAs QD ordering on top in spotlike arrays of isolated QD molecules, down to single QDs in the center, due to local strain recognition. More complex architectures of QD arrays have been created on shallow-and deep-etched artificially patterned substrates.…”

Coherent acoustic phonons in strain engineered InAs∕GaAs quantum dot clusters

“…High quality QDs in well-defined arrangements, such as QD arrays [3][4][5] and ordered QD groups, [6][7][8][9] have been realized by self-organized strain engineering. The number of QDs within a single group or QD cluster, formed by using strained-layer superlattice ͑SL͒ templates, 7,8 is controlled by varying the growth temperature of the SL template and the thickness of the GaAs separation layer between the SL template and the QD layer. 8 A consequence of strained nanostructure growth is the strongly enhanced piezoelectric ͑PZE͒ field, 10,11 which in turn affects the electro-optical properties of the structure.…”

“…[11][12][13][14] In this letter, we report on the differential reflectivity of QDs arranged in a small ordered group of four QDs per cluster on average, grown by strain engineering. 7,8 Using pump-probe time-resolved differential reflection spectroscopy ͑TRDR͒, 15 we are able to measure the carrier capture and carrier relaxation process, and the carrier recombination process within the QDs. For structures with a random QD distribution, the decay of the TRDR signal is described by a single exponential function.…”