Defect creation in Ge and GaAs semiconductor crystals by huge electronic excitations: a thermal spike description

Irradiation of semiconductor crystals with swift heavy ions or cluster beams is one way of obtaining information about both the defect characteristics in the investigated material and the defect formation mechanisms. In this work, to explain the formation of defects (latent tracks) observed experimentally to be effects of cluster-ion irradiations in Ge and GaAs, we have used the thermal spike model. The part of the energy used for thermal spike formation is determined by the electron-phonon coupling constant, g, which is unknown for semiconductors. The thermal spike calculations performed with an electron-phonon coupling constant, g(300 K) = 1.8 x 10¹² W cm^-3K^-1 for Ge and g(300 K) = 3.2 x 10¹² W^-3cm^-3K^-1 for GaAs nicely reproduce the size of amorphous tracks observed in both materials irradiated with C₆₀ clusters, assuming the quenching of a vapor phase as the criterion of track formation. Our results also show that g decreases when the electronic stopping power threshold increases. The expected propensity, electron-phonon coupling increasing with the band gap energy, is confirmed. (author)