Solid phase epitaxy of stressed and stress-relaxed Ge-Si alloys

Abstract

Solid phase epitaxy of 3500-Å-thick GexSi1−x (0.04≤x≤0.12) films on (100) Si substrates has been investigated. The thickness of regrown layers increased linearly with annealing time in the temperature range of 475–575 °C. The regrowth rates of stressed alloys were less than those of pure Si, while stress-relaxed alloys have larger rates than Si. The difference in regrowth rates was explained by the activation-strain tensor model (Aziz, Sabin, and Lu, to be published in Phys. Rev. B). The first element of the activation-strain tensor obtained in this experiment was in excellent agreement with that deduced by Aziz et al. For low Ge concentrations (x<0.08), the recrystallized region was of good crystalline quality. However, threading dislocations were observed in a stressed Ge0.1Si0.9 alloy after complete recrystallization. During the regrowth at 550 °C, the Ge-Si alloy first regrew coherently up to 300 Å, above which threading dislocations started to nucleate. On the other hand, no dislocations were detected in the regrown layer of a stress-relaxed Ge0.1Si0.9 alloy sample.