Iron doping of InP and GaInAsP( lambda g=1.05 mu m) layers grown by metalorganic molecular beam epitaxy was studied using elemental source material in combination with a conventional effusion cell. This study was aimed at the creation of semi-insulating optical waveguides under growth conditions compatible with selective area growth. Secondary ion mass spectroscopy measurements revealed a reproducible and homogeneous incorporation behavior of the iron dopant in the materials investigated. Resistivities in excess of 109 Omega cm were obtained for both compositions at medium doping levels. GaInAsP/InP waveguide structures grown at 485 degrees C-the minimum temperature necessary for selective deposition-exhibited averaged resistivities of 5*107 Omega cm in combination with optical losses of 2.5+or-0.5 dB/cm.