Photoreflectance study of surface photovoltage effects at (100)GaAs surfaces/interfaces

We report a photoreflectance study of surface photovoltage (VS) effects on the determination of Fermi level pinning (VF) on (100) n-GaAs in air and with W-metal coverage (in situ) as a function of temperature (77 K<T<450 K) and light intensity (I). The dependence of VS on T and I can be explained by a modification the theory of M. Hecht [Phys. Rev. B 41, 7918 (1990)] yielding a value of VF=0.73±0.02 V. The effect of metal coverage is to reduce the influence of VS.