A traveling-wave photodetector (10, 22, 30) having a waveguide layer (12) separated, such as by an intermediate layer (24), from an absorbing layer (14). Absorbed power is spread out, minimizing thermal heating of the photodetector (10, 22, 30). Light travels through a weakly absorbing optical waveguide (12) and the electrical current generated by the absorbed light is collected by electrodes (18, 36). The juxtaposition of the waveguide layer (12) and the absorbing layer (14) eliminates electron and hole trapping allowing high-power and large bandwidth operation of the traveling-wave photodetector (10, 22, 30).