Influence of Substrate Temperature on Epitaxial Growth of Ge on Si by Sputtering

27th European Photovoltaic Solar Energy Conference and Exhibition; 298-300
Ge wafers have been used as substrates for the growth of III–V based tandem solar cells because of the ideal lattice match. However, Ge wafers are high cost and the bandgap of Ge is too small which limits its contribution to the voltage output. Using epitaxial Ge on Si as template for III–V growth is a promising solution. Si has much higher bandgap and lower cost than Ge. Epitaxial Ge film with low dislocation density and smooth surface is desired for III–V growth. Since the substrate temperature could significantly influence the film property, it is investigated to optimize the deposition condition for Ge epitaxial growth. To compare the microstructure of the Ge films deposited at different substrate temperatures, the surface morphology was analyzed by atomic force microscopy (AFM), structural property of the films was examined by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). Ge film deposited at high substrate temperature exhibits good crystallinity, low dislocation density and rough surface.