Polarization-independent broadband absorption enhancement of thin-film InGaAs photodetector

The trade-off between the enhanced signal-to-noise ratio and reduced light absorption in thin-film photodetectors is the main issue for improving device performance. Nanoscale patterning of metal/dielectric interface can couple incident light into surface plasmon polaritons (SPPs) modes, leading to the enhanced absorption. However, due to the nature of resonant excitation of SPPs, it is difficult to realize broadband absorption enhancement. In this study, we propose a novel device structure to achieve absorption enhancement over the whole spectral response range of the thin-film In0.53Ga0.47As photodetector. Numerical simulation shows that both the preferential forward scattering of InP cylinder and grating coupled waveguide modes contribute to the broadband absorption enhancement.