Melt depth and regrowth kinetics in pulsed laser annealing of silicon and gallium arsenide

High intensity pulsed laser irradiation of semiconductor materials results in ultrafast melting and resolidification of a thin surface layer. An experimental probe has been developed based on the discontinuous change in electrical conductivity of a semiconductor material upon melting. Real time monitoring of the dynamics of pulsed laser melting and resolidification can be obtained by transient electrical conductance measurements. Melting velocities from 5 to 200 m/s and resolidification velocities of 1 to 20 m/s have been observed in silicon with this technique. Simultaneous measurement of the optical reflectance provides additional complementary information on laser melting dynamics. Data from both electrical conductance and optical reflectance measurements are presented for silicon and gallium arsenide. The real time experimental data provide strong evidence for a simple thermal model for melting and resolidification during nanosecond pulsed laser annealing