Zinc incorporation by post-growth metal-organic vapor phase epitaxy (MOVPE) based diffusion, also called metalorganic vapor phase diffusion (MOVPD), using diethylzinc (DEZ) as precursor into InP and InAs0.60P0.40 epitaxial layers has been studied systematically. Both the InP and InAS(0.60)P(0.40) epitaxial layers are grown with low pressure MOVPE. High hole concentrations of respectively 1.7 x 10(19) and 6 x 10(18)/cm(3) are obtained for InAs0.60P0.40 and InP. Diffusion depths were measured using cleave-and-stain techniques, electrochemical profiling, resistivity measurements and secondary ion mass spectroscopy. Hall measurements were also used to determine the hole concentrations. The diffusion depth can be controlled reproducibly within the investigated range from 0.5 to over 2.0 mum. The diffusion coefficients for InP and InAs0.60P0.40 were derived and the influence of the dislocation density of the InP and InAs0.60P0.40 layers on the Zn diffusion process was investigated, through epitaxial growth on different substrate orientations.