Single Crystalline Ge Thin Film Grown on C-Plane Sapphire by Molecular Beam Epitaxy

Germanium (Ge) film was grown on c-plane sapphire with and without a 10 nm AlAs buffer layer using molecular beam epitaxy. The samples were characterized using high-resolution X-ray diffraction (HRXRD) and atomic force microscopy (AFM). The samples grown directly on sapphire exhibits 2 germanium orientations, the (111) and (220) while samples grown using the AlAs buffer layer had only (111) orientation at 27.5 degrees. Samples that were grown with the AlAs buffer were investigated further and at different temperatures were observed to relax the compressive strain as the temperature was increased. From the Phi scan, the peaks with high intensity appear after every 60 degrees while lower intensity peaks can be seen at 30 degrees between the high intensity peaks. We also investigate the impact of different the thickness (50nm, 100nm,150nm and 200 nm) of the Ge layer. In this case the ratio of the high to low intensity Phi scan peaks was less with 100 nm thick Ge sample. This sample also had the lowest XRD rocking curve linewidth of 633 arcsec. This sample is prepared for epitaxy growth of SiGe and GeSn and we will discuss initial efforts at these growths.