Adatom Diffusion at GaN (0001) and (000bar1) Surfaces

TL;DR

This study uses density-functional theory to compare Ga and N adatom diffusion on GaN surfaces, revealing significant differences in mobility that impact growth conditions and surface stabilization.

Contribution

It provides detailed insights into the diffusion behaviors of Ga and N adatoms on GaN surfaces, highlighting the effects of excess N on diffusion barriers.

Findings

Ga adatoms are highly mobile at typical growth temperatures.

N adatoms diffuse much slower than Ga adatoms.

Excess N increases the Ga diffusion barrier.

Abstract

The diffusion of Ga and N adatoms has been studied for the technologically relevant wurtzite (000bar1) and (0001) surfaces employing density-functional theory. Our calculations reveal a very different diffusivity for Ga and N adatoms on the equilibrium surfaces: While Ga is very mobile at typical growth temperatures, the diffusion of N is by orders of magnitudes slower. These results give a very detailed insight of how and under which growth conditions N adatoms can be stabilized and efficiently incorporated at the surface. We further find that the presence of excess N strongly increases the Ga diffusion barrier and discuss the consequences for the growth of GaN.