Abstract: Epitaxial germanium film on silicon substrates has been extensively investigated for its potential applications in opto-electronic integration due to its pseudo-direct band structure, small bandgap,large absorption coefficient, high carrier mobility, and most importantly, compatibility with Si complementary metal oxide semiconductor processing.We review the recent progress in the heteroepitaxial growth of Ge films on Si substrates, as well as potential applications in optoelectronics, especially in long wavelength photodiodes and lasers.Growth techniques including the use of compositionally varied SiGe buffers,selective epitaxy and low temperature are presented.The dependence of performance on the structure of Ge-on-Si photodiodes is discussed.The impact of tensile strain and n-type doping on the optical properties of Ge is analyzed, and the outlook for monolithically integrated and electrically pumped Ge-on-Si lasers is given.