A kinetic study of InP:Fe growth has been carried out in a low pressure hydride vapor phase epitaxy (LP-HVPE) reactor using Ferrocene as iron source. The influence of the ferrocene partial pressure on the growth behavior has been investigated. A drastic decrease of the growth rate in the presence of ferrocene has been experimentally measured. This effect is explained to be due to cyclopentadiene adsorption. A kinetic model, that takes into account this adsorption, is proposed, which explains the observed experimental results.