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 illumination is studied by electrical conductivity and Hall effect experiments at different excitation wavelengths. Ultraviolet illumination at room temperature 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 weak barrier exists for the dissociation of Si-H(D) complexes under UV excitation. Moreover, a strong isotope effect is observed in the dissociation kinetics of these complexes at 300 K and 100 K for low photon densities. We propose that the UV illumination induces an electronic excitation of Si-H complexes in GaAs. The strong isotope effect is discussed in the light of recent electronic excitation models of Si-H(D) bonds at the surface of silicon. (C) 2000 Academic Press.