Stability of wurtzite semi-polar surfaces: algorithms and practices

TL;DR

This paper introduces a first-principles computational approach to accurately determine the absolute surface energies of wurtzite semi-polar surfaces, crucial for understanding and controlling the morphology of semiconductor nanostructures.

Contribution

It presents a general algorithm for calculating absolute formation energies of semi-polar surfaces, addressing previous challenges caused by structural asymmetry and complex reconstructions.

Findings

Achieved accuracy within 1.5 meV/Ų for calculated surfaces

Provided comprehensive surface energy data for GaN semi-polar surfaces

Fills a technical gap in understanding compound semiconductor shapes

Abstract

A complete knowledge of absolute surface energies with any arbitrary crystal orientation is important for the improvements of semiconductor devices because it determines the equilibrium and nonequilibrium crystal shapes of thin films and nanostructures. It is also crucial in the control of thin film crystal growth and surface effect studies in broad research fields. However, obtaining accurate absolute formation energies is still a huge challenge for the semi-polar surfaces of compound semiconductors. It mainly results from the asymmetry nature of crystal structures and the complicated step morphologies and related reconstructions of these surface configurations. Here we propose a general approach to calculate the absolute formation energies of wurtzite semi-polar surfaces by first-principles calculations, taking GaN as an example. We mainly focused on two commonly seen sets of semi-polar surfaces: a-family (11-2X) and m-family (10-1X). For all the semi-polar surfaces that we have calculated in this paper, the self-consistent accuracy is within 1.5 meV/{\AA}^2. Our work fills the last technical gap to fully investigate and understand the shape and morphology of compound semiconductors.