Deposition of thin epitaxial films is required for the fabrication of many microelectronic devices. Often, these layers must be patterned by photolithographic processes, whereupon further layers are deposited to build up complex structures. Selected-area growth of thin films would greatly simplify this procedure. Consequently, there has been considerable interest in laser-assisted direct-white epitaxy. It is known that an argon ion laser, compared to an excimer laser, is easier to operate and does not cause the problem of plastic deformation of crystal lattices associated with large thermal stresses. In this report, an Ar+-laser (488 nm) is used to assist metalorganic (chemical beam epitaxy of phosphides and doped GaAs. In addition, results from Ar+-laser assisted epitaxy are analyzed. Lateral variations in growth rates, doping levels and compositions of epitaxial layers have been successfully induced with laser irradiation. To investigate the mechanisms responsible for the observed laser-induced effects, numerical models for chemical beam epitaxy have been developed in this work. It is demonstrated that properly combining reaction schemes derive from surface-science desorption studies enables us to predict well the growth rate and doping concentration without adjustable parameters.