Abstract
A temperature activated crossover between two nucleation regimes is observed in the behavior of Ga droplet nucleation on vicinal GaAs(111)A substrates with a miscut of 2° towards (bar{1}bar{1}2). At low temperature (<400 °C) the droplet density dependence on temperature and flux is compatible with droplet nucleation by two-dimensional diffusion. Increasing the temperature, a different regime is observed, whose scaling behavior is compatible with a reduction of the dimensionality of the nucleation regime from two to one dimension. We attribute such behavior to a presence of finite width terraces and a sizeable Ehrlich-Schwöbel barrier at the terrace edge, which hinders adatom diffusion in the direction perpendicular to the steps.
Highlights
Fundamental DE-QD properties, volume and density, are controlled by the droplet characteristics
Samples were grown with an molecular beam epitaxy (MBE) system, equipped with a valved cell for As4 supply, on a semi-insulating GaAs(111)A substrates with a miscut of 2° towards (112)
Via atomic force microscope (AFM) measurements we have determined that the GaAs buffer layer consists of terraces separated by step with height in the 1–3 ML range
Summary
Fundamental DE-QD properties, volume and density, are controlled by the droplet characteristics. We show the presence, on GaAs(111)A substrates with a miscut of 2° towards (112), of a temperature activated crossover in the dimensionality of the scaling parameters that controls the dependence of droplet density N on F and T from two to one dimension. We correlate such crossover to the presence of the temperature activated onset of a restriction in the adatom diffusion related to the presence of regular and finite width terraces and steps. The latter, due to the associated Ehrlich-Schwoebel (ES) barrier[11], induce a strong spatial anisotropy in the adatom diffusivity at the origin of the dimensionality change
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