Novel diffusion mechanism on the GaAs(001) surface: the role of adatom-dimer interaction

TL;DR

This study uses first principles calculations to reveal a novel diffusion mechanism of Ga and Al adatoms on GaAs(001), showing two distinct channels with different dimer interactions that lead to anisotropic diffusion behavior.

Contribution

It introduces a new understanding of adatom diffusion on GaAs(001) surface, highlighting two diffusion channels with different dimer interactions and their impact on diffusion anisotropy.

Findings

Diffusion is anisotropic, fastest parallel to surface dimers.

Al adatoms have higher diffusion barriers than Ga.

Two distinct diffusion channels involve different dimer interactions.

Abstract

Employing first principles total energy calculations we have studied the behavior of Ga and Al adatoms on the GaAs(001)-beta2 surface. The adsorption site and two relevant diffusion channels are identified. The channels are characterized by different adatom-surface dimer interaction. Both affect in a novel way the adatom migration: in one channel the diffusing adatom jumps across the surface dimers and leaves the dimer bonds intact, in the other one the surface dimer bonds are broken. The two channels are taken into account to derive effective adatom diffusion barriers. From the diffusion barriers we conclude a strong diffusion anisotropy for both Al and Ga adatoms with the direction of fastest diffusion parallel to the surface dimers. In agreement with experimental observations we find higher diffusion barriers for Al than for Ga.