Shadow‐masked growth using organometallic vapor‐phase epitaxy allows the creation of nonplanar regions having smoothly varying profiles devoid of macroscopic facets. The shape of these profiles is independent of gas flow direction and stripe orientation, suggesting that they are determined by lateral gas phase gradients. It is proposed that the absence of facets is due to the unique growth regime underneath the shadow mask, where organic radicals combine with group‐III surface species, temporarily returning them to the vapor phase. This process has been simulated using a two‐dimensional finite‐element analysis that accurately describes the experimental behavior. Furthermore, this hypothesis predicts other experimentally observed phenomena. ©1995 American Institute of Physics.