Molecular dynamics simulation of crystal growth in [formula omitted] (100) heterostructures

Abstract

Pulsed laser-induced liquid phase epitaxy of SiGe alloy/pure Si substrate heterostructures, exposing both (100) and (111) orientations, has been studied by nonequilibrium molecular dynamics (NEMD) simulation techniques using Stillinger-Weber potential models for the two components. Solid-liquid interfacial morphology, the quality of the regrown materials and Ge redistribution at the interface were studied under both fast and slow recrystallization conditions, controlled by the substrate temperature. For the (100) orientation, a significantly non-planar solid-liquid interface was found for all Ge concentrations, with Ge atoms at the bottom of this interfacial “well”, causing solidification to be retarded in their vicinity. For the (111) orientation, in-plane defects with alternating structures of two five-membered rings and one eight-membered ring were found in the regrown material due to the unstable growth kinetics on the “back” side of the interface response function. At slow crystallization rates, only stacking defects were found in the regrown material, without in-plane defects. The Ge partition coefficient obtained from simulation at slow regrowth speeds is in good agreement with experimental measurements and also agrees well with the prediction of Aziz's continuous growth model if the Ge diffusivity at the solid-liquid interface and the width of the interface are used in the calculation of the “diffusive velocity”.