Heteroepitaxial passivation of GaAs surfaces and its influence on the photosensitivity spectra and recombination parameters of GaAs epitaxial layers and semi-insulating materials

We investigate the influence of heteroepitaxial passivation of GaAs surfaces by a thin lattice matched InGaP layer on the spectra of photomagnetic effect, planar photoconductivity and capacitor photovoltage in conducting layers and semi-insulating substrates of GaAs. Reduction of the surface recombination rate by one or two orders of magnitude at passivation of layer surfaces simplifies significantly determination of their recombination parameters by photoelectric methods and enables one to get an insight into the nature of the phenomena causing the decrease of photosensitivity in a strong absorption region. We revealed a strong influence of the state of the surface on recombination parameters of semi-insulating GaAs: the ambipolar diffusion length and the magnitude and ratio of electron to hole components of photoconductivity. Surface passivation changes this ratio towards domination of the electron component