Having grown semiconductor-on-insulator (SOI) layers by liquid phase epitaxy (LPE) we have investigated their properties by x-ray topography, optical-, atomic force- and high resolution electron microscopy and by etching experiments.
A first series of experiments was carried out on (111)-oriented Si substrate wafers which were partially masked by thermal oxide. Area- selective LPE, which was then applied and followed by epitaxial lateral overgrowth (ELO), yielded SOI layers of high quality. Silicon SOI layers had aspect ratios of up to 65 and were typically dislocation-free. These highly perfect SOI structures facilitated studies of the specific processes for semiconductor lateral growth over amorphous layers. Vertical stresses were detected in the substrate-layer systems. They were found to influence the shapes of the SOI layers. Our studies suggest that here is a model case for solution growth of thin semiconductor lamellae on dissimilar substrates.
Subsequently, a second series of experiments consisted in having SiGe lamellae grown in the same fashion. These experiments confirm that the same morphology is observed for Ge-contents up to 2 percent.