Development of morphological instability and formation of cells in silicon alloys during pulsed laser irradiation

Abstract

The details of morphological instabilities occuring during rapid solidification have been studied in In +, Sb +, Ga + and Bi + implanted silicon after pulsed laser annealing. Interfacial instability results in lateral segregation of impurities, which leads to the formation of cellular structures. The average cell sizes, at the onset of instability (OI) and in the region of well-developed instability (DI), were determined using plan-view and cross-section electron microscopy. Total and substitutional solute concentration profiles were determined using high resolution Rutherford backscattering, ion channeling techniques. The formation of cells and the critical solute concentrations associated with instability were studied as a function of velocity of solidification by varying either the substrate temperature or the laser parameters. Results on the cell formation and the critical solute concentrations were compared with calculations of the perturbation theory in which experimentally deduced values of distribution coefficients and liquids slopes were used. A good agreement was obtained between the calculations and the ecperimental results on critical solute concentrations, and between the calculations and the OI cell sizes, which were larger than those in the DI region.