A mathematical model was developed to examine the growth rate of Ill -V compounds inside sub micron trenches by MOVPE. Based on this model, we theoretically analyzed the possible dependence of the growth rate on the trench width primarily from two aspects, i.e. Knudson diffusion and enhanced equilibrium vapor pressure due to the shrinking trench size. Then, associated with the experimental data from the growth of both InAlAs and InAs, we found that the average growth rate inside submicron trenches is primarily influenced by trench diffusion type under typical growth conditions. (C) 2014 Elsevier BM. All rights reserved