Kinetic model of element Ⅲ segregation during molecular beam epitaxy of Ⅲ-Ⅲ′-Ⅴ semiconductor compounds

摘要

Segregation of column Ⅲ atoms during molecular beam epitaxy of Ⅲ-Ⅲ'-Ⅴ semiconductor compounds causes nonabrupt interfaces and a surface composition different from the bulk one. To derive concentration profiles, a thermodynamical equilibrium model has been used for a long time. This model applies well to describe segregation processes at high growth temperatures, but fails in predicting concentration profile variations with substrate temperature. We have thus developed a kinetic model which correctly takes into account the evolution with the growth temperature. We apply this model to the case of indium segregation in the Ga_xIn_(1-x)As/GaAs system. The calculated indium concentration profiles are compared to those obtained with the thermodynamical equilibrium model. A kinetic limitation of segregation is shown to appear at low substrate temperatures and sufficiently high growth rates. This limitation is predicted to arise below 400℃ for a growth rate of 1 monolayer/s for In segregation in the Ga_xIn_(1-x)As/GaAs system.