Realization and characterization of thin single crystal Ge films on sapphire

Abstract

We have successfully produced and characterized thin single crystal Ge films on sapphire substrates (GeOS). Such a GeOS template offers a cost-effective alternative to bulk germanium substrates for applications where only a thin (<2 µm) Ge layer is needed for device operation. The GeOS templates have been realized using the Smart CutTM technique. 100 mm diameter GeOS templates have been manufactured and characterized to compare the Ge thin film properties with bulk Ge. Surface defect inspection, SEM, AFM, defect etching, XRD and Raman spectroscopy were all performed. The results obtained for each characterization technique used have highlighted that the material properties of the transferred thin Ge film were very close to the ones of a bulk Ge reference. An epitaxial AlGaInP/GaInP/AlGaInP double heterostructure was grown atop the GeOS template to demonstrate the template's stability under the conditions encountered in typical device realization. The photoluminescent behavior of this epitaxial structure was nearly identical to that of a similar structure grown on a bulk Ge substrate. The GeOS templates therefore offer a viable alternative to bulk Ge substrates in the fabrication of devices whose operation is compatible with a thin film structure.