Optical communications networks must be terminated by receiver circuitry capable of converting an optical circuit to an electrical one. While current III-V technology is capable of delivering high performance, it is costly and difficult to integrate with low-cost Si based technologies. In order to overcome these barriers, we are pursuing a Si-compatible technology for integrated photodetectors. Ge, monolithically integrated with Si, offers a low-cost, high-performance materials system for photodetector integration with existing Si technology. In this paper we discuss the performance requirements and figures of merit for integrated photodetectors. We then discuss the materials issues associated with the integration of Ge on Si and show that high quality Ge films can be grown directly on Si, despite the 4% lattice mismatch. By cyclic annealing after growth, the dislocation density can be reduced to 2.3x107 cm-2, and diodes fabricated on these films show a responsivity of 300 mA/W at 1300 nm without an AR coating. Finally, we discuss the integration of waveguides with photodetectors and propose an integration scheme we believe will be capable of delivering high-performance integrated photoreceivers on a Si platform.