The surface phase transition on GaAs(0 0 1) was investigated in real time by core-level photoelectron spectroscopy and reflection high-energy electron diffraction (RHEED). The time dependence of the relative surface band bending was obtained from the deconvolution of core-level photoelectron spectra. We found that band bending on the 4 x 2 surface increases 0.06 eV from that of the 2 x 4 surface and that the time dependence of relative surface band bending is in good agreement with that of core-level photoelectron intensities but not with the RHEED intensities. This indicates that the long-range ordering of surface superstructures and microscopic surface morphology does not influence surface band bending, whereas the termination atoms, As or Ga, does. (C) 2004 Elsevier B.V. All rights reserved.