Integration of photonic devices on silicon (Si) substrates is a key method in enabling large scale manufacturing of Si-based photonic–electronic circuits for next generation systems with high performance, small form factor, low power consumption, and low cost. Germanium (Ge) is a promising material due to its pseudo-direct bandgap and its compatibility with Si-CMOS processing. In this article, we present our recent progress on achieving high quality germanium-on-silicon (Ge/Si) materials. Subsequently, the performance of various functional devices such as photodetectors, lasers, waveguides, and sensors that are fabricated on the Ge/Si platform are discussed. Some possible future works such as the incorporation of tin (Sn) into Ge will be proposed. Finally, some applications based on a fully monolithic integrated photonic–electronic chip on an Si platform will be highlighted at the end of this article.