Plasmonic Nanoparticles on Graphene Absorber for Broadband High Responsivity 2D/3D Photodiode

To overcome the image deterioration caused by pixel miniaturization resulting from the high-resolution trend of CIS (CMOS image sensor) technology, a photodiode working with an enhanced mechanism based on a distinctive device structure from the existing one is considerably required. In this study, our photodiode, consisting of gold nanoparticles/monolayer graphene/n-type trilayer MoS₂/p-type Si bulk, achieved ultrafast rising/falling times of 28.6 ns/30.4 ns due to the spatially confined narrow depletion width (DW) resulting from the 2D/3D heterojunction. To compensate for the expected low absorbance due to the narrow DW, plasmonic gold nanoparticles on monolayer graphene are introduced, revealing broadband enhanced EQE of an average of 187% in the spectral range of 420-730 nm and the maximum EQE reaching 847% at 5 nW for a 520 nm wavelength. The broadband enhancement was further investigated through multiphysics simulation, and carrier multiplication in graphene was discussed for the reason for exceeding 100% EQE in our reverse biased photodiode.