Pulsed-laser annealing of GaAs surface studied by time-resolved second-harmonic generation in reflection

Experimental results are presented on the time dependence of the second-harmonic generation (SHG) of a mode-locked Q-switched Nd: YAG laser in reflection from both amorphous and crystalline GaAs surfaces during the pulsed-laser annealing under ruby laser irradiation. A dramatic increase of SHG by more than two orders of magnitude due to recrystallization of the noncentrosymmetric GaAs lattice in the process of pulsed-laser annealing is observed and the duration of surface recrystallization is measured to be not greater than 30–40 ns. The results can be fully understood in terms of the melting model of laser annealing.