Clean and As-covered zinc-blende GaN (001) surfaces: Novel surface structures and surfactant behavior

TL;DR

This study uses first-principles calculations to reveal novel surface structures of GaN (001) and demonstrates arsenic's potential as an effective surfactant, impacting growth properties.

Contribution

It uncovers a new stable surface structure for GaN (001) involving a Peierls distortion and identifies arsenic as a beneficial surfactant for surface energy reduction.

Findings

Most stable clean surface involves a Peierls distortion.

As coverage significantly lowers surface energy.

Identified mechanisms influencing surface structures.

Abstract

We have investigated clean and As-covered zinc-blende GaN (001) surfaces, employing first-principles total-energy calculations. For clean GaN surfaces our results reveal a novel surface structure very different from the well-established dimer structures commonly observed on polar III-V (001) surfaces: The energetically most stable surface is achieved by a Peierls distortion of the truncated (1x1) surface rather than through addition or removal of atoms. This surface exhibits a (1x4) reconstruction consisting of linear Ga tetramers. Furthermore, we find that a submonolayer of arsenic significantly lowers the surface energy indicating that As may be a good surfactant. Analyzing surface energies and band structures we identify the mechanisms which govern these unusual structures and discuss how they might affect growth properties.