Inversion Domain Boundaries in Wurzite GaN

TL;DR

This paper introduces two new atomic models for inversion domain boundaries in wurzite GaN, demonstrating that one model is energetically favorable and potentially observed in experiments, along with an improved energy calculation method.

Contribution

It proposes two novel atomic models for inversion domain boundaries in wurzite GaN and an improved method for calculating domain wall energies.

Findings

One model has lower formation energy than Holt-$IDB$.

The new model can form under typical growth conditions.

An improved energy calculation method was developed.

Abstract

We present two models for the atomic structure of inversion domain boundaries in wurzite GaN, that have not been discussed in existing literature. Using density functional theory, we find that one of these models has a lower formation energy than a previously proposed model known as Holt-$IDB$. Although this newly proposed model has a formation energy higher that the accepted lower energy structure, known as $IDB^*$, we argue that it can be formed under typical growth conditions. We present evidence that it may have been already observed in experiments, albeit misidentified as Holt-$IDB$. Our analysis was facilitated by a convenient notation, that we introduced, to characterize these models; it is based on the mismatch in crystal stacking sequence across the $\{10\overline{1}0\}$ plane. Additionally, we introduce an improved method to calculate energies of certain domain walls that challenge the periodic boundary conditions needed for plane-wave density functional theory methods. This new method provides improved estimations of domain wall energies.