TEMPERATURE-INDUCED CHANGES IN OPTICAL-PROPERTIES OF THE LIQUID-PHASEDURING NANOSECOND LASER MELTING OF SILICON AND GERMANIUM

Complex refractive indices of liquid silicon and germanium in the temp erature ranges of thermodynamic stability of the liquid state have bee n calculated by two methods, by structure factor modeling and using th e specific electrical conductivities of the melts. Time-resolved refle ctivity 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. Th e calculated data based on structure factor modeling agree better with experiment for germanium than for silicon. The experimental data indi cate that significant overheating, by several hundred degrees, of the liquid phase by nanosecond laser melting of diamond-like semiconductor s is quite feasible. (C) 1996 American Institute of Physics.