Microstructure Simulation Study Of GaAs Directional Solidification Growt

Gallium arsenide(GaAs)is one of the most widely used III-V compound semiconductor material with superior electrical and optical properties.The preparation of high-quality GaAs crystals is an important basis for the development of high frequency microwave electronic devices and light emitting devices.The microstructure of the material determines the macroscopic properties,so the study of the microstructure during the growth of GaAs crystals is particularly critical.In this paper,the directional solidification growth behavior of GaAs under different conditions was simulated by molecular dynamics(MD)simulation,and the crystallization process and microstructure evolution mechanism were deeply investigated.Firstly,the directional solidification growth of GaAs along the three crystal orientations [100],[110] and [111] was simulated by molecular dynamics.The vast majority of melt atoms are induced by seed crystals in all three crystal orientations to form crystal structures dominated by [4-S000] La SC clusters.Except for the [100]crystal orientation,the other two systems form wurtzite structures that compete with the sphalerite structures.At the same temperature,the shape of the solid-liquid interface is overall flatter when growing along the [100] crystal direction,but the solid-liquid interface along the [110] direction moves the fastest.Due to the dense packing structure of the(111)plane,the crystallization effect and crystal growth rate of the [111] crystal orientation system are the lowest,and there is a high probability of dislocation nucleation in the grown crystals,where there is a companion relationship between1/6<112> partial dislocations and twins.Secondly,the process of oriented crystal growth of GaAs melt at eight different temperatures was simulated with the aim of discussing the effect of temperature on microstructure formation during [111] orientation-induced crystallization.It was found that the quality of the crystals grown at low temperatures was not ideal,with a high density of dislocations and defective atoms.The higher temperatures are to some extent more favorable to the crystallization of the melt part and the lamellar structures of sphalerite and wurtzite structures are formed in the system.Moreover,the higher the temperature or the lower the degree of under cooling,the lower the dislocation density.At the temperature of 1700 K,the solid-liquid model of GaAs induces the highest crystallization rate and the best quality crystals,and the initially formed dislocations in the system gradually slip to the crystal surface and be eliminated.Finally,the effect of stress or strain on the growth of GaAs along the [110]direction of directional solidification was investigated.It was found that the crystal growth was inhibited at the initial stage after applying a certain tensile strain and a larger compressive strain,and the larger the strain,the lower the crystallization rate.The zigzag interface during crystal growth is bounded by {111} small planes,and the angle between it and the growth plane influences the morphology of the solid-liquid interface and the formation of twins.The larger the applied tensile strain,the smaller the angle,the more twin defects will form and the more irregular they will be.Moreover,the strain can inhibit or promote the nucleation of dislocations,and a suitable strain size can make the crystal grow without dislocation.When the relative compressive strain is-2%,the dislocation density is significantly reduced and the crystal formed in the system is the most standard.