Enhancement of Photodetector Responsivity and Response Speed Using Cascaded-Cavity Structure with Subwavelength Metallic Slit

A cascaded-cavity photodetector with subwavelength metallic slit is proposed to enhance responsivity and response speed simultaneously.Responsivity enhancement depends on light transmittance increased by using a subwavelength metallic slit plasmonic mode resonant cavity;it also relies on quantum efficiency improved by adopting a resonant cavity enhanced structure.Response speed improvement is due to low capacitance of metal-slit-metal and thin absorption layers.In the cascaded-cavity structure,the subwavelength metallic slit plays a vital role in performance improvements.Simulation results show that,for the optimized slit structure,responsivity enhancement of 80 times can be achieved compared to the conventional structure.In addition,response bandwidth of the optimized structure can reach 150 GHz.