In this paper, the design of resonant cavity enhanced photodetectors, working at 1.55 micron and based on silicon technology, is reported. The photon absorption is due to internal photoemission effect over the Schottky barrier at the metal-silicon interface. A comparison is presented among three different photodetectors having as Schottky metal: gold, aluminium or copper respectively. In order to quantify the performance of photodetector, quantum efficiency including the image force effect, as a function of bias ...