Surface photovoltage spectroscopy of real n-type GaAs(110) surfaces

N-type GaAs single crystals cut parallel to the (110) plane and doped with phosphorus by ion beam implantation were used in the present study. Temperature dependence of the bulk electrical conductivity showed two distinct activated regions with activation energies Et sub 1 =0.75 + or - 0.04eV, and Et sub 2 =0.12 + or - 0.04eV. The first activation energy is probably that of deep phosphorous impurities, while the second was related to long range disorder in the sample near room temperature. Surface photovoltage studies at room temperature were carried out at atmospheric pressure and in vacuum for etched and unetched samples. For n-type GaAs etched surface, the experimentally observed surface states were not found to change their positions by changing the pressure. But in the case of etched samples the surface states showed some redistribution under vacuum. The time constants for the initial rise and fall of CPD by illumination and after switching it off, tau sub 1 and tau sub 2, respectively, were found to depend on the illumination intensity and photon energy. Their values range between 4 and 15 s.