Study On Nanoclusters In Rapid Solidification Of Liquid InGaAs

The group III-V compound semiconductor material,which has excellent optical and electrical properties,is a second generation semiconductor material after silicon material,and it is considered to be one of the most important materials for today's optoelectronic and electronic devices.The macroscopic properties of the materials are determined by their microstructures.Under the existing experimental conditions,it is difficult to observe and analyze the microstructure of InGaAs during melting and solidification.It is of great significance to trace the microstructure evolution of InGaAs during melting and solidification by computer simulation.In this paper,the melting process,the rapid solidification process and the rapid solidification process under different pressures of In0.5Ga0.5As were simulated by molecular dynamics method.The Tersoff potential function,which had been proved to be suitable for the simulation of the complex InxGa1-xAs covalent bond system,was used for calculation,and the radial distribution function(RDF),angle distribution function(ADF),coordination number(CN)and visualization were used to analyze the microstructures evolution characteristics of InGaAs during melting process and rapid solidification.The analysis of the microstructure evolution of the ideal InGaAs crystal during the melting process shows that: The first-order phase transition in the melting process occurs near 1280 K.At this time,the covalent bond between the atoms is broken,the structure of the main coordination number changes from the four-coordinated structure to the three-coordinated structure,and the microstructure in the solid-liquid phase transition process has great changes.In the process of melting,through the dominant coordination of the three-coordination structure,combined with a small amount of four-coordination structure,the interconnection is formed between three-coordination and three-coordination structure,at the same time,a topological disordered liquid structure is also formed through intertwined connection between three-coordination and four-coordination structure.The microstructures of liquid InGaAs during rapid solidification at different cooling rates show that: crystallization is not occurred in liquid In GaAs under five different cooling speeds and the final form of the system is amorphous,which indicates that the formation ability is very strong for the amorphous of ternary alloy.The effect of cooling rate on the solidification process of InGaAs is as follows: With the decrease of the cooling rate,the order structure of the system is gradually enhanced and the number of three-coordinated structure increase in some way.At the same cooling rate,with the decrease of temperature,the short range order is also improved.The microstructure of liquid InGaAs during rapid solidification at different pressures was analyzed.The results show that the pressurization has a great influence on the arrangement of atoms in the nearest neighbor and next nearest neighbor.The increase of the pressure makes the atomic arrangement of the system more compact,and the short range order of the system is improved.With the increase of the pressure,the coordination number of the system changes from the three-coordination structure to the four-coordination structure,and the arrangement of atoms is more compact,which makes the arrangement of the RDF next nearest neighbor atoms more concentrated.In addition,for the rapid solidification process of liquid InGaAs,it is found that the effect of temperature on the structure is much less than that of the pressure in the pressurization process.The first principles pseudo-potential plane wave method was used to calculate the structure of two-dimensional In0.5Ga0.5As graphenelike.The results show that two types of graphite configuration does not exist of the Ga atom as the center,surrounded by In,In,As atoms and As atoms around In,As,As.But in the case of Ga atom as the center,surrounded by three As atoms of optimized graphenelike structure,the arrangement of the atoms appears large changes,the distribution of atoms are not in the same plane.