The spontaneous patterning of epitaxially growing surfaces is studied in the framework of two-species models of step Row. designed to describe epitaxial deposition in complex systems as compound semiconductors MBE, MOVPE and HVPE. Self-organisation follows from step-edge potential energy barriers, as well as from the coupling of the diffusing species at the crystal surface. The characteristic length-scales of surface patterns such as ridges and step bunches are investigated with kinetic Monte Carlo simulations, and analytic estimations as a functions of growth parameters are proposed. The present analysis can be considered as an efficient tool for guiding the experimental control of surface patterning.