Electronic processes in laser-induced Ga0emission and laser ablation of the GaP(110) and GaAs(110) surfaces
- 4 April 1994
- journal article
- Published by IOP Publishing in Journal of Physics: Condensed Matter
- Vol. 6 (14) , 2697-2712
- https://doi.org/10.1088/0953-8984/6/14/008
Abstract
We have carried out sub-monolayer sensitivity measurements of laser-induced Ga0 emission from the GaP(110) and GaAs(110) surfaces using a resonant ionization technique. The laser ablation threshold fluence is defined as the critical fluence above which an increase of the Ga0 emission yield is observed by repeated irradiation with laser pulses on the same spot but below which a decrease of the yield is observed. The photon-energy dependences of the laser ablation threshold fluence and the sub-ablation emission yield have been investigated for photons below, near and above the bulk band-gap energies in both GaP and GaAs. For photons below the band-gap energies, the sub-ablation emission and laser ablation are observed and ascribed to photon absorption by defects on the surfaces. The sub-ablation emission is found to be reduced substantially at a photon energy slightly below the band-gap energies for both GaP and GaAs; the reduction is of resonance type for GaAs and stepwise for GaP. Only a small amount of emission is observed for GaP for photons above the band-gap energy. The ablation threshold fluence for GaAs shows a resonant-type increase, corresponding to me resonance-type reduction of the sub-ablation emission yield, while the ablation threshold fluence for GaP does not change on crossing the band-gap energy. For photons above the band-gap energies, the ablation threshold fluence decreases with increasing photon energy in a similar manner for both GaP and GaAs. The decrease in the ablation threshold fluence for the GaAs(110) surface appears to be correlated to the increase in the sub-ablation emission yield as observed previously. These results of the photon energy dependence of the sub-ablation emission yield and ablation threshold fluence are explained in terms of the electronic excitation of defects on surfaces and of surface occupied states.Keywords
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