Long time evolution of meandered steps during the crystal growth processes

TL;DR

This study uses kinetic Monte Carlo simulations to analyze how step meandering evolves during gallium nitride crystal growth, revealing different behaviors depending on temperature and particle flux, with implications for surface morphology control.

Contribution

It introduces a model incorporating four-body interactions to simulate step meandering during crystal growth, highlighting the effects of flux and temperature on meander formation and evolution.

Findings

High temperatures and low fluxes preserve straight steps.

Higher fluxes induce meandering with shorter wavelengths.

Two distinct meandering regimes with different time behaviors.

Abstract

Step meandering during growth of gallium nitride (0001) surface is studied using kinetic Monte Carlo method. Simulated growth process, conducted in N-rich conditions are therefore controlled by Ga atoms surface diffusion. The model employs dominating four-body interactions of Ga atoms that cause step flow anisotropy during growth. Overall kinetics and shape selection features of step meandering are analyzed assuming their dependence on the external particle flux and on the temperature. It appears that at relatively high temperatures and low fluxes steps move regularly preserving their initial shapes of straight, parallel lines. For higher fluxes and at wide range of temperatures step meandering happens. It is shown that, depending on the initial surface parameters, two different scenarios of step meandering are realized. In both these regimes meandering has different character as a function of time. For relatively high fluxes meanders have wavelengths shorter than the terrace width and they grow independently. Eventually surface ends up as a rough structure. When flux is lower regular pattern of meanders emerges. Step meander even if Schwoebel barrier is absent. Too high barrier destroys step stability. The amplitude of wavelike step meanders increases in time up to a saturation value. The mechanism of such meander development is elucidated.