Laser induced phase transitions in Si and Ge implanted Si substrates

Computer calculations based on the Fourier equation of the heat flow are reported for ruby and excimer laser irradiation of silicon substrates implanted with Ge and Si ions. The calculated thresholds for the epitaxial crystallization are compared to the experimental values determined by Rutherford backscattering spectrometry (RBS) and channeling measurements. Good agreement is achieved between calculated and experimental values for ruby laser irradiation of Si and Ge implanted samples, while for the excimer laser irradiation of Ge implanted samples the numerical simulations do not agree with the experimental values. A reduced reflectivity of the surface during the melting of the Ge implanted samples must be considered in order to reproduce the experimental data. The study indicates that a complicated melting dynamics occurs during laser irradiation with the excimer laser with an inhomogeneous melting caused by the Gaussian Ge concentration profile.