ON THE THEORY OF LASER SPUTTERING THROUGH PAIRING OF HOLES IN COMPOUND SEMICONDUCTORS

A simple kinetic model is used to explain the observed dependence of the sputtering quantum yield on the laser fluence. The mechanism of sputtering presented here involves pairing of two holes against their repulsive Coulomb barrier, which depends on the concentration of photoexcited charge carriers through Debye screening. A threshold laser fluence is obtained at a concentration of photoexcited charge carriers that suppresses the barrier sufficiently to allow the pairing of holes at the surface bonds. The bonds are broken and atoms are ejected from the surface. The temperature dependence of the threshold laser fluence is discussed. Results agree qualitatively with experiments and existing theories.