Enhanced radial growth of Mg doped GaN nanorods: A combined experiment and first-principles based analysis

TL;DR

This study combines experimental electron microscopy and first-principles calculations to reveal that magnesium doping enhances the radial growth of GaN nanorods by reducing surface free energy and diffusion barriers, leading to increased surface coverage and coalescence.

Contribution

It provides a detailed microstructural and theoretical analysis explaining how Mg doping promotes radial growth in GaN nanorods, which was not previously understood.

Findings

Mg increases surface coverage and reduces nanorod height.

Mg doping promotes coalescence of nanorods at lower heights.

First-principles calculations show reduced surface free energy and diffusion barriers with Mg doping.

Abstract

We discuss the microstructural origin of enhanced radial growth in magnesium (Mg) doped gallium nitride (GaN) nanorods (NRs) using electron microscopy and \textit{first-principles} Density Functional Theory calculations. Experimentally, we find the Mg incorporation increases surface coverage of the grown samples and the height of NRs decreases as a consequence of an increase radial growth rate. We also observed the coalescence of NRs becomes prominent and the critical height of coalescence decreases with the increase in Mg concentration. From \textit{first-principles} calculations, we find the surface free energy of Mg doped surface reduces with increasing Mg concentration in the samples. The calculations further suggests a reduction in the diffusion barrier of Ga adatoms along [11$\overline{2}$0] on the side wall surface of the NRs, possibly the primary reason for the observed enhancement in the radial growth.