SOLID-PHASE EPITAXY OF STRESSED AND STRESS-RELAXED GE-SI ALLOYS

Solid phase epitaxy of 3500-angstrom-thick GexSi1-x (0.04 less-than-or-equal-to x less-than-or-equal-to 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-degrees-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-degrees-C, the Ge-Si alloy first regrew coherently up to 300 angstrom, 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.