Photodetectors using Si, Ge and their alloys with other group IV elements are of current interest for application in telecommunication as well as in optical interconnects. We have presented in this paper our work on resonant cavity enhanced Si/SiGe multiple Quantum Well and Ge Schottky photodetectors. Calculated values of external quantum efficiency for GeSiC based photodetectors are also reported. Tensile strained Ge layers grown with suitable barriers show direct gap type I band alignment. Predicted performance of photodetectors using strong Quantum Confined Stark Effect and Franz-Keldysh Effect in these structures and properties related to photodetection using these new materials are also described.Keywords Photodetectors · Ge/SiGe quantum wells · Direct gap in Ge · Quantum confined stark effect · Franz Keldysh effect · GeSn and SGeSn alloys