Surface photovoltage and photoelectron spectra of GaP

Surface photovoltage (SPV) and photoelectron spectra (PES) of crystalline n -GaP wafers have been studied at 300 K. The magnitude of the surface potential ( V s ) decreases in the presence of photons with energy more than the band gap, however the magnitude of V s increases in the presence of photons with sub band gap energy. The SPV spectrum is helpful in understanding the rigid shift of PES spectra of n -GaP wafers towards higher kinetic energy in the presence of secondary white light from a tungsten lamp.