Details of the structural and electrical properties of epitaxial DyP/GaAs and DyAs/GaAs are reported. DyP is lattice matched to GaAs, with a room temperature mismatch of less than 0.01%. Both DyP and DyAs have been grown by solid source molecular beam epitaxy. High quality DyP and DyAs epilayers, as determined by x-ray diffraction, transmission electron microscopy, and atomic force microscopy analyses, have been obtained for growth temperatures ranging from 500 to 600 degrees C and growth rates between 0.5 and 0.7 mu m/h. DyP epilayers are n type with measured electron concentrations on the order of 3-4 x 10(20 )cm(-3), room temperature mobilities of 250-300 cm(2)/V s, and a barrier height of 0.81 eV to n-type GaAs at room temperature. DyAs epilayers are also n type with measured electron concentrations of 1-2 x 10(21) cm(-3) and mobilities between 25 and 40 cm(2)/V s. DyP is stable in air with no apparent oxidation taking place, even after months of ambient exposure to untreated air.