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We fabricated fully strained Si0.77Ge0.23epitaxial layers on Si substrates and investigated their strain relaxation behaviors under dry oxidation and the effect of oxidation temperatures and times. After the oxidation process, a Ge-rich layer was formed between the oxide and the remaining Si0.77Ge0.23layer. Using reciprocal space mapping measurements, we confirmed that the strain of the Si0.77Ge0.23layers was efficiently relaxed after oxidation, with a maximum relaxation value of ~ 70% after oxidation at 850 °C for 120 min. The surface of Si0.77Ge0.23layer after strain relaxation by dry oxidation was smoother than a thick Si0.77Ge0.23layer, which achieved a similar strain relaxation value by increasing the film thickness. Additionally, N2 annealing was performed in order to compare its effect on the relaxation compared to dry oxidation and to identify relaxation mechanisms, other than the thermally driven ones, occurring during dry oxidation.

In this study, we investigated the formation of a Si1−xGexfin structure in SiO2trench arrays via an ultra-high-vacuum chemical-vapor deposition (UHV-CVD) selective epitaxial growth (SEG) process. Defect generation and microstructures of Si1−xGexfin structures with different Ge concentrations (x= 0.2, 0.3 and 0.45) were examined. In addition, the strain evolution of a Si1−xGexfin structure was analyzed by using reciprocal space mapping (RSM). An (111) facet was formed from the Si1−xGexepi-layer and SiO2trench wall interface to minimize the interface and the surface energy. The Si1−xGexfin structures were fully relaxed along the direction perpendicular to the trenches regardless of the Ge concentration. On the other hand, the fin structures were fully or partially strained along the direction parallel to the trenches depending on the Ge concentration: fully strained Si0.8Ge0.2and Si0.7Ge0.3, and a Si0.55Ge0.45strain-relaxed buffer. We further confirmed that the strain on the Si1−xGexfin structures remained stable after oxide removal and H2/N2post-annealing.