In this paper, the design of a novel photodetector, working at 1.55 µm and completely silicon compatible, is reported. The device is a resonant cavity enhanced (RCE) structure incorporating a silicon photodetector based on the internal photoemission effect. In order to quantify the performance of photodetector, quantum efficiency including the image force effect as a function of bias voltage are analytically calculated. Moreover we propose a comparison among three different Schottky barrier Silicon photodetectors, having as metal layers gold, silver or copper, respectively.