Raman scattering experiments were carried out on Si∕SiGe heterostructures. The strain in both the top Si layer, and the Si1−xGex buffer layers with various Ge compositions was evaluated using several excitation sources, together with x-ray diffraction and secondary ion mass spectrometry. The strain-shift coefficient, which is a necessary quantity to evaluate the strain by Raman spectroscopy, was precisely determined. The dependence of the Si–Si band frequency on the Ge composition in the SiGe alloy was also examined. We found that the strained top-Si layers with a thickness below 25nm experience coherent growth on Si1−xGex buffer layers with composition x<0.35.

SiGe-on-insulator substrate fabricated by melt solidification for a strained-silicon complementary metal-oxide-semiconductor J.Effects of H + implantation ͑ഛ5 ϫ 10 16 cm −2 ͒ on stress relaxation in an oxidation-induced Ge condensation method have been investigated to form stress-relaxed ultrathin ͑ϳ30 nm͒ SiGe-on-insulator ͑SGOI͒ virtual substrates. High-dose ͑ജ10 15 cm −2 ͒ implantation enhanced stress relaxation, which was attributed to bond breaking at the SiGe/ buried SiO 2 interface. However, oxidation velocity was also enhanced due to irradiation defects. Two-step annealing ͑500°C for 30 min and 850°C for 60 min͒ before oxidation was proposed to remove irradiation defects. This achieved enhanced stress relaxation in ultrathin SGOI without changing oxidation velocity.

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Interface states density (Nss) and minority carrier generation lifetime (τg) were evaluated for strained Si(St-Si)∕SiGe wafers using deep level transient spectroscopy and metal-oxide-semiconductor transient capacitance methods. Nss shows an independence on St-Si thickness (dSi) and an obvious dependence on Ge fraction (Ge%). τg shows a strong dependence on both dSi and Ge%. The reasons of these dependencies are discussed in detail.

Strain-relaxation process of SiGe-on-insulator (SGOI) structures in the oxidation induced Ge condensation method has been investigated as a function of the SiGe thickness. Complete relaxation was obtained for thick SGOI layers (>100nm). However, the relaxation rates abruptly decreased with decreasing SiGe thickness below 50nm, i.e., the relaxation rate of 30% at 30nm SiGe thickness. In order to improve this phenomenon, a method combined with H+ irradiation with a medium dose (5×1015cm−2) and postannealing (1200°C) has been developed. This successfully achieved the high relaxation rate (70%) in the ultrathin SGOI (30nm).