Pulsed laser irradiation of GaAs under oxygen and silane atmosphere: Incorporation, losses, influence of native oxide

Gallium arsenide single crystals and thin GaAs amorphous deposits (in the 100-nm range) on Si have been irradiated by pulsed (15 ns) ruby laser under various pressures of 16O2. All the samples were anodically preoxidized in order to obtain a 10-nm-thick 18O enriched oxide, the aim being to study the influence of native oxide on oxygen incorporation during irradiation. Nuclear microanalysis and channeling experiments provide information on (i) 16O incorporation, (ii) 18O losses and concentration profile, (iii) Ga and As atoms out of crystallographic sites for single crystal irradiations, and (iv) Ga and As losses for thin films irradations. Our results demonstrate that a surface oxide is formed with a composition near the Ga2O3-As2O3 stoichiometry via oxygen penetration in the melted layer once the native oxide has been evaporated at irradiation energies above 1 J/cm2. Before complete evaporation,this latter oxide diffuses in GaAs and is responsible for defect creation at irradiation energies as low as 0.4 J/cm2. We also find that for irradiation in vacuum the surface composition varies continuously, from Ga to As rich, when the irradiation energy density goes from 0.4 to 1.5 J/cm2. Pulsed irradiations at 0.53 μm under silane atmosphere lead to strong Si doping. We show that the mechanism involved is pyrolisis of SiH4, surface deposition of the Si formed and finally diffusion of the deposited layer in GaAs during melting.