Enhanced absorption of silicon microholes array via filling with HgSe/PbS quantum dots and graphene films for long-wave infrared light detection

Two-dimensional (2D) nanomaterials and narrow bandgap colloidal quantum dots (CQDs) have attracted broad interest due to their exceptional advantages such as their high photoresponsivity, easy processing and tunable bandgap by controlling its size. Achieving high absorption in long-wave infrared (LWIR) region requires to design the device structures skillfully and to maximize light trapping in photodetectors, thus to enhance charge carriers’ separation and to suppress charge carriers’ recombination. In this work, enhanced absorption of LWIR light from IR photodetector Al/Si-MHs/[(HgSe/PbS)/graphene]/Al, in which HgSe/PbS core/shell CQDs and graphene films are filled into the micropores array sequentially, is presented via synergistic combining the surface plasmon resonance (SPR) effect and the enhanced charge separation. As a result, a high optical absorption close to 100 % in LWIR region (∼16 µm) is obtained from the photodetector Al/Si-MHs/[(HgSe/PbS)(4 μm)/ graphene(2 μm)]/Al, with an external quantum efficiency (EQE) of 77.45 % and a specific detectivity of 4.58 × 10¹² Jones. Also, our experimental results on HgSe/PbS quantum dots and their applications in IR photodetectors Au/(HgSe/PbS)/Au confirm the LWIR absorption ability of HgSe/PbS core/shell QDs. Thus, our results show a promising feasible method for next-generation flexible LWIR photodetectors.