Temperature-induced changes in optical properties of the liquid phase during nanosecond laser melting of silicon and germanium

Complex refractive indices of liquid silicon and germanium in the temperature ranges of thermodynamic stability of the liquid state have been calculated by two methods, by structure factor modeling and using the specific electrical conductivities of the melts. Time-resolved reflectivity of the liquid phase formed by nanosecond ruby laser heating of semiconductors has been studied using probe radiation at wavelengths of 0.53 or 1.06 mu m and optical pyrometry has been used to determine the peak temperature as a function of the radiation energy density. The calculated data based on structure factor modeling agree better with experiment for germanium than for silicon. The experimental data indicate that significant overheating, by several hundred degrees, of the liquid phase by nanosecond laser melting of diamond-like semiconductors is quite feasible. (C) 1996 American Institute of Physics.