Indium segregation during III-V quantum wire and quantum dot formation on patterned substrates

TL;DR

This paper develops a reaction-diffusion model for the epitaxial growth of InGaAs nanostructures on non-planar substrates, explaining facet-dependent kinetics and growth outcomes, including quantum wire and dot formation.

Contribution

It introduces a comprehensive kinetic model for III-V nanostructure growth on patterned substrates, incorporating facet-dependent processes and explaining experimental observations.

Findings

Model accurately predicts InGaAs nanostructure growth on non-planar surfaces.

Identifies facet-dependent kinetic parameters for InGaAs epitaxy.

Reveals new facetting phenomena at pyramidal recesses facilitating quantum dot formation.

Abstract

We report a model for metalorganic vapor-phase epitaxy on non-planar substrates, specifically V-grooves and pyramidal recesses, which we apply to the growth of InGaAs nanostructures. This model, based on a set of coupled reaction-diffusion equations, one for each facet in the system, accounts for the facet-dependence of all kinetic processes (e.g., precursor decomposition, adatom diffusion, and adatom lifetimes) and has been previously applied to account for the temperature, concentration, and temporal-dependence of AlGaAs nanostructures on GaAs (111)B surfaces with V-grooves and pyramidal recesses. In the present study, the growth of In$_{0.12}$Ga$_{0.88}$As quantum wires at the bottom of V-grooves is used to determine a set of optimized kinetic parameters. Based on these parameters, we have modeled the growth of In$_{0.25}$Ga$_{0.75}$As nanostructures formed in pyramidal site-controlled quantum-dot systems, successfully producing a qualitative explanation for the temperature-dependence of their optical properties, which have been reported in previous studies. Finally, we present scanning electron and cross-sectional atomic force microscopy images which show previously unreported facetting at the bottom of the pyramidal recesses that allow quantum dot formation.