Evolution mechanism of the topological structure during solid-liquid phase transition of InGaAs crystal

Abstract

Melting refers to the phase transition from solid to liquid, which is a common physical phenomenon in nature. It is also a phase transformation process that the materials such as metals and semiconductors need to undergo in the process. It is closely related to the preparation and performance of materials. At present, it is difficult to trace the microstructure of the melting process, and computer simulation can get a lot of microstructure information of the melting process, which can well explain how the orderly arrangement of crystals becomes random liquid phase structure in the melting process. For the ternary semiconductor alloy In x Ga1 - x As, it has important application value in microelectronics and optoelectronic devices, because it can adjust its electrical parameters and optical band gap in a wide range composition. So the research of alloy structure has been paid more and more attentions for the ternary semiconductor. It is generally known that the macroscopic properties of the materials are mainly determined by their microstructures. However, most studies on the melting process are based on the dynamics, but the mechanism of the evolution of the microstructure during the melting process is lacking. Therefore, it is of great significance to study the evolution of microstructures during the melting process of InGaAs crystals in the development of novel optoelectronic materials and devices. At present, it is still difficult in the experiment to obtain the structural details of InGaAs system during the melting process. Molecular dynamics simulation is an efficient tool especially for such process. In this paper, the melting process of the ideal InGaAs crystal is simulated by using the molecular dynamics method, and the Tersoff potential function of the In x Ga1 - x As covalent bond system, which has been proved to be suitable for the simulation of complex structures. The structural evolution of the solid-liquid phase transition process was analyzed by using the radial distribution function, angular distribution function, coordination numbers and 3D visualization. From the results of our simulation, we find that the microstructures of the InGaAs phase change greatly during the solid-liquid phase transition, especially in the first-order phase transition. It shows significant variations in the average atomic energy and specific volume, the radial distribution function, angular distribution functions, coordination numbers and atomic cross-sections, local atomic distributions, and diamond structure analysis. In the melting process, covalent bonds the InGaAs atoms are broken, and the system changes from the four coordinated structure into the three coordinated structure. For the dominant three coordinated structure and a small amount of four coordinated structures, the three coordinated structure is connected with the three coordinated structure, and the three coordinated structure interpenetrated the four coordinated structure to form a disordered topological structure.