Characterization of Semiconductor Films Epitaxially Grown on Thin Metal Oxide Buffer Layers

Abstract

Silicon and germanium films epitaxially grown on metal oxide buffer layers on Si(111) substrates are characterized by different X-ray techniques, transmission electron microscopy and Raman spectroscopy. Pr2O3 and Y2O3 or a combination of both is used as buffer material. X-ray pole figure measurements and grazing incident X-ray diffraction prove that epi-semiconductor layers can be grown single crystalline with exactly the same in-plane orientation as the Si(111) substrate. Epi-Ge layers show a small fraction (less than 0.5 vol. %) of so-called type B rotation twin regions located near the oxide-Ge interface. The main structural defects for both epi materials are micro twin lamellas lying in {111} planes 70° inclined to the wafer surface that may reach through the whole layer from the oxide interface to the surface. Furthermore, TEM confirms the existence of stacking faults and threading dislocations. X-ray grazing incident diffraction and Raman measurements show that epi-Ge layers on Pr2O3 buffer are nearly fully relaxed, while epi-Si layers on Y2O3/Pr2O3 double buffer are compressive strained depending on their own thickness and the thickness of the underlying Y2O3 layer. It is demonstrated that the epi-layer quality can be improved by post-deposition annealing procedures.