In this paper we present a general methodology for the design of resonant cavity enhanced (RCE) photodetectors based on the internal photoemission effect. In order to estimate the theoretical quantum efficiency we take advantage of the analytical formulation of the internal photoemission effect (Fowler theory), and its extension for thin films. In particular, the absorptance is numerically determined by means of an approach based on the transfer matrix method. Finally, we apply the proposed methodology to the design of a silicon RCE photodetector operating at 1.55μm, based on the internal photoemission effect at an Au-Si schottky barrier.