Ab-Initio calculations of binding energy of In and Ga adatoms on three GaAs(111)A surface reconstructions

TL;DR

This study uses ab-initio calculations to compare the binding energies and diffusion barriers of Ga and In adatoms on different GaAs(111)A surface reconstructions, elucidating conditions for heterostructure growth.

Contribution

It provides detailed ab-initio insights into adatom-surface interactions on GaAs(111)A surfaces, highlighting the importance of the As trimer surface for In adsorption and heterostructure formation.

Findings

Ga adatom has stronger bond energy than In adatom.

Diffusion barriers for Ga are higher on the Ga vacancy surface.

As trimer surface favors In adsorption for hetero-interface formation.

Abstract

Calculations of the potential energy surface for tracer Ga and In adatoms above three GaAs (111)A surface reconstructions are presented in order to understand the growth conditions required to form axial heterostructures in GaAs/InGaAs nano-pillars. In all calculations the Ga adatom has a stronger bond energy to the surface than the In adatom. The diffusion barriers for Ga adatoms are 140meV larger than for In adatoms on the Ga vacancy surface, but they are comparable on the As trimer surface. Also the binding energy for an In adatom is closer to that of a Ga adatom on the As trimer surface. We conclude that the As trimer surface is preferable for adsorption of In and thus for selective formation of hetero-interfaces on (111) facets. This work helps explain the recent successful formation of axial GaAs/InGaAs hetero-interfaces in catalyst free nano-pillars.