Influence of cooling rate on microstructure and defect evolution in GaAs during solidification

The fabrication of high-quality GaAs crystals is essential to approach optimal performance in optoelectronic and microelectronic devices. In this study, a molecular dynamics simulation study was conducted for the solidification of liquid GaAs at three cooling rates (1010 K s-1, 1011 K s-1, and 1012 K s-1) at 300 K. The structural evolution in terms of crystal structure and defect formation in GaAs was thoroughly investigated using pair distribution function, average atomic energy, the largest standard cluster analysis, and visualization techniques. The results showed that the cooling rate of 1010 K s-1 led to the development of the best crystal quality with ease of eutectic twin grain boundary coherent twin boundary formation. Increasing the cooling rates to 1011 K s-1 and 1012 K s-1 resulted in the amorphous structure. Both high and low cooling rates profoundly affected the formation of As8 structure, but a maximum amount of 2.2% of As8 crystal structure was formed at a cooling rate of 1011 K s-1. The reduction in cooling rate to 1010 K s-1 induced the formation of numerous Schottky and Frenkel types of partial dislocations in the GaAs system. Results of this study can serve as potential guidelines to the theory of crystal growth and may be implemented in the fabrication of high-quality GaAs crystals for optimal device performance.