The redistribution and diffusion of vanadium in V‐doped high resistivity bulk as‐grown GaAs, in V‐doped GaAs ion implanted with V, and in high purity epitaxial layers grown on top of V‐doped substrates upon various thermal annealing processes are compared to that of Cr using secondary ion mass spectrometry. The thermal processes studied are typical for GaAs IC technology. V diffuses by one order of magnitude less than Cr in all cases investigated. Thus, from thermal stability point of view V‐doped GaAs substrates should be superior to Cr‐doped ones and probably also to the present so‐called ‘‘undoped’’ ones containing 1016cm−3EL2 compensators.