The Effect of III:V Ratio on Compositional and Microstructural Properties of GaAs1-xBix (001)

Abstract Compound semiconductors alloyed with Bi have many interesting properties, but the low solubility of Bi in these materials leads to effects such as Bi segregation and the formation of surface droplets. To study these effects, a series of GaAsBi films were grown as a function of growth conditions, namely the Bi:As and As:Ga flux ratios. Four surface morphologies emerged—surfaces that were free of droplets, contained Bi droplets, Ga droplets, or biphasic Ga/Bi droplets—as a function of flux ratio. Further analysis with X- ray diffraction, Transmission Electron Microscopy, and Atomic Probe Tomography revealed specific microstructures corresponding to the types of droplets present. Finally, we propose a model to explain each microstructure that takes into consideration factors including Ga adatom diffusion, bulk Bi diffusion, Bi droplet mobility, and film growth rate.