Metropolis Monte Carlo based Relaxation of Atomistic III-V Semiconductor Models

Abstract

We present atomistic simulations of III-V semiconductor materials. These provide an effective way to investigate structural properties of semiconductors at a nanometric scale. The crystal structure is relaxed using a Metropolis Monte Carlo scheme, where chemical bonds are described through empirical interaction potentials. The method provides a simplified structural model, which allows to determine elastic properties like the bulk and shear modulus with errors around 5 and 10 %. Simulations on random alloys led to a composition-dependent bimodal bond length distribution, stemming from the constituent binary compounds, which was also observed experimentally. In contrast to this, CuPt-ordered structures, which can form spontaneously during epitaxial processes, were shown to exhibit a distinct fourfold bond length pattern leading to built-in strain. The Metropolis Monte Carlo approach also allows modelling at higher temperatures. The asymmetry of the empirical potential function leads to thermal expansion, although this effect is in general overestimated due to the missing Coulomb interaction, which is characteristic of III-V materials.