Spiral growth of a multicomponent crystal from vapor of its components

•BCF theory is expanded to growth of a multicomponent crystal from vapors of its components.•Rate of advance of a group of equidistant steps and crystal spiral growth rate are derived.•Growth can be described in terms of generalized coefficients which depend on properties of each component. The classical BCF theory is extended for the description of the spiral growth of a multicomponent crystal from vapor of its components. Equations for the rate of advance of a group of equidistant steps are derived. The spiral growth rate of the crystal is found. It is shown that the growth of the multicomponent crystal can be described mathematically in the same way as the growth of a single-component crystal using a few generalized parameters: diffusion coefficient, supersaturations, each of which depends on properties of all individual crystal components. As an example, the theory is applied to describe gallium nitride crystal growth.