Strong isotope effects in the ultraviolet light-induced reactivation of dopants in hydrogenated or deuterated n-GaAs : Si

The reactivation of silicon donors in hydrogenated n-GaAs:Si under illumina tion is studied by electrical conductivity and Hall effect experiments at d ifferent excitation wavelengths. Ultraviolet illumination at room temperatu re of hydrogenated n-GaAs:Si by photons with energies above 3.5 eV is found to be an efficient alternative way to reactivate silicon donors. A very we ak barrier exists for the dissociation of Si-H(D) complexes under UV excita tion. Moreover, a strong isotope effect is observed in the dissociation kin etics of these complexes at 300 K and 100 K for low photon densities. We pr opose that the UV illumination induces an electronic excitation of Si-H com plexes in GaAs. The strong isotope effect is discussed in the light of rece nt electronic excitation models of Si-H(D) bonds at the surface of silicon. (C) 2000 Academic Press.