Self-ordered nanostructures on patterned substrates

Abstract

The formation of nanostructures during metalorganic vapor-phase epitaxy on patterned (001)/(111)B GaAs substrates is reviewed. The focus of this review is on the seminal experiments that revealed the key kinetic processes during nanostructure formation and the theory and modelling that explained the phenomenology in successively greater detail. Experiments have demonstrated that V-groove quantum wires and pyramidal quantum dots result from self-limiting concentration profiles that develop at the bottom of V-grooves and inverted pyramids, respectively. In the 1950s, long before the practical importance of patterned substrates became evident, the mechanisms of capillarity during the equilibration of non-planar surfaces were identified and characterized. This was followed, from the late 1980s by the identification of growth rate anisotropies (i.e. differential growth rates of crystallographic facets) and precursor decomposition anisotropies, with parallel developments in the fabrication of V-groove quantum wires and pyramidal quantum dots. The modelling of these growth processes began at the scale of facets and culminated in systems of coupled reaction-diffusion equations, one for each crystallographic facet that defines the pattern, which takes account of the decomposition and surface diffusion kinetics of the group-III precursors and the subsequent surface diffusion and incorporation of the group-III atoms released by these precursors. Solutions of the equations with optimized parameters produced concentration profiles that provided a quantitative interpretation of the time-, temperature-, and alloy-concentration dependence of the self-ordering process seen in experiments.

Next generation low temperature polycrystalline materials for above IC electronics. High mobility n- and p-type III–V metalorganic vapour phase epitaxy thin films on amorphous substrates

“…3.1. Growth protocol MOVPE is a non-trivial, multistep process where substrates have a catalytic role enabling the precursors' decomposition and subsequent material growth [11]. We emphasize this aspect here, as it is both relevant for the interpretation of what we report, and is rarely underlined in mainstream discussions of MOVPE processes.…”

Vanishing biexciton binding energy from stacked, MOVPE grown, site-controlled pyramidal quantum dots for twin photon generation

“…PQDs are fabricated starting from a patterned (111)B-oriented GaAs substrate (in which tetragonal recesses are obtained), on which MOVPE is performed depositing InGaAs dots with GaAs barriers, as for example discussed in ref [25] and [26]. The growth process is the interesting result of the competition between precursors decomposition rate anisotropies, and adatom diffusion and preferential attachment at concave recesses (also referred to in the literature as capillarity processes) [27] [28]. More details on the fabrication procedure of the stacked system can also be found in ref.…”

“…concave recesses (also referred to in the literature as capillarity processes) [27] [28]. More details on the fabrication procedure of the stacked system can also be found in ref.…”

Phase-field method for epitaxial kinetics on surfaces

“…Another extension is deposition and decomposition polyatomic molecules that contain the atomic constituents of the growing film, which is the basis of metal-organic vaporphase epitaxy. The application of the phase field method to this growth scenario on surfaces patterned with V-grooves or inverted pyramids, 94 whose facets have different properties, would enable computations on the scale of nanostructure arrays that would complement modeling based on reaction-diffusion equations. 95…”