Optimization procedure for the design of ultrafast, highly efficient and selective resonant cavity enhanced Schottky photodiodes

An expression of quantum efficiency for high-speed resonant-cavity-enhanced (RCE) Schottky photodiodes is derived. This expression includes the structural and the physical parameters of the photodetector and takes into account the parameters of the metallic Schottky mirror and the wavelength dependence of the reflectivities. The metal layer thickness sets the maximum achievable quantum efficiency as it decays exponentially with it. The antireflection coating layer, on the other hand, determines the photodetector selectivity and the optimum absorption layer thickness that maximizes its quantum efficiency. An algorithm for the design and optimization of RCE Schottky photodetectors has been developed. Theoretical values of 647 GHz and 129 GHz were obtained, respectively, for the carrier-transit time limited 3-dB bandwidth and bandwidth-efficiency product for an RCE Schottky photodetector with a 0.02 μm gold layer.