Double step structure and meandering due to the many body interaction at GaN(0001) surface in N-rich conditions

TL;DR

This paper models GaN(0001) surface growth under N-rich conditions using Monte Carlo simulations, revealing how many-body interactions cause step anisotropy, double terrace formation, and surface meandering phenomena observed in experiments.

Contribution

It demonstrates the impact of four-body interactions and external conditions on step dynamics and surface morphology during GaN growth, linking simulation results to experimental observations.

Findings

Double terrace structures form due to step flow anisotropy.

Step meandering and surface roughening depend on diffusion barriers.

High flux conditions lead to triangular island formation.

Abstract

Growth of gallium nitride on GaN(0001) surface is modeled by Monte Carlo method. Simulated growth is conducted in N-rich conditions, hence it is controlled by Ga atoms surface diffusion. It is shown that dominating four-body interactions of Ga atoms can cause step flow anisotropy. Kinetic Monte Carlo simulations show that parallel steps with periodic boundary conditions form double terrace structures, whereas initially V -shaped parallel step train initially bends and then every second step moves forward, building regular, stationary ordering as observed during MOVPE or HVPE growth of GaN layers. These two phenomena recover surface meandered pair step pattern observed, since 1953, on many semiconductor surfaces, such as SiC, Si or GaN. Change of terrace width or step orientation particle diffusion jump barriers leads either to step meandering or surface roughening. Additionally it is shown that step behavior changes with the Schwoebel barrier height. Furthermore, simulations under conditions corresponding to very high external particle flux result in triangular islands grown at the terraces. All structures, emerging in the simulations, have their corresponding cases in the experimental results.