A method of controlling the relative amounts of silicon dopant inside and outside of an enhanced growth region on an indium phosphide substrate using a metalorganic chemical vapor deposition (MOCVD) process. The method includes the steps of positioning the indium phosphide substrate in a reactor chamber, and defining an enhanced growth region on the substrate by depositing a dielectric mask on the substrate. The indium phosphide substrate is heated to a growth temperature of between about 600 and 630° C., and the pressure in the reactor chamber is adjusted to between about 40 and 80 Torr. A first gas contains a metalorganic compound comprising indium and a hydrogen carrier gas flow of between about 12 and 16 liters/minute, and a second gas containing a phosphide and a doping gas containing a silicon dopant at a flow rate of between are introduced into the reactor chamber. The first and second gases are mixed in the chamber and forced over the substrate in a laminar flow such that the mixed convection parameter is between about 0.31 and 0.33. An n-type indium phosphide epitaxial layer is thereby grown over the substrate by reacting the first with the second gas and thermally decomposing the carrier gas, whereby areas inside and outside of the growth enhanced region contain substantially the same amount of silicon dopant.