The electrical properties of p-type layers of indium phosphide (InP), formed by the diffusion of zinc into n-type material, are studied by Hall Effect measurements. A wide range of diffusion conditions are used and both homogeneously doped specimens and those containing a zinc atom concentration gradient are produced. A non-correspondence of atom and carrier concentrations is indicated, confirming previous four point resistivity studies. Carrier profiles are achieved by both serial sectioning and multiple specimen techniques. Contacting procedures are developed from which plots of carrier mobility versus carrier concentration, in the range 5 x 1017 - 5 x 1019 cm – 3, are produced for p-n-p InP. In the main, present results showed good reproducibility and conformed to the "rules" of the Van der Pauw technique.