This paper focuses on UV-photodetector simulation. The calculus method description and the physical equations which occur in this model are presented as well as the UV-photodetector structure (p+n--n+ diode). Based on the Finite Element Method the electrical part solves the continuity and Poisson equation, and the optical part solves by Maxwell’s equation, FDTD . Simulation works point out the influence of the p+-type layer on the electrical characteristics such as the current densities versus reverse bias. Indeed, simulation results show the current density increase with the decrease doping concentration or the p+-type layer thickness.