Macroscopic theory of pulsed-laser annealing. II. Dopant diffusion and segregation

The radiation from Q-switched ruby and Nd:YAG (yttrium aluminum garnet) lasers can anneal the lattice damage produced by ion implantation of semiconductors. In the first paper of this series, we described the models and methods we have been using for heat-transport calculations during pulsed-laser annealing and gave numerous illustrations of the type of results which are obtained. In this paper, we discuss dopant-diffusion calculations in detail, with particular emphasis on the incorporation of segregation effects into the modeling. From the forms of the experimental dopant profiles, it is established that pulsed-laser annealing is a nonequilibrium process, but in this paper the interface segregation coefficient is treated as an adjustable parameter and no attempt is made to justify the values obtained. Approximate analytical and finite-difference solutions to the diffusion equation are discussed and compared. It is argued here that the excellent fit between theory and experiment which is obtained is a strong indication of the basic validity of the melting model of pulsed-laser annealing